diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiClient.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiClient.kt.mustache
index 934cf63524d0..8b7d4f3b665e 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiClient.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiClient.kt.mustache
@@ -5,11 +5,11 @@ import java.io.File
 
 open class ApiClient(val baseUrl: String) {
     companion object {
-        protected val ContentType = "Content-Type"
-        protected val Accept = "Accept"
-        protected val JsonMediaType = "application/json"
-        protected val FormDataMediaType = "multipart/form-data"
-        protected val XmlMediaType = "application/xml"
+        protected const val ContentType = "Content-Type"
+        protected const val Accept = "Accept"
+        protected const val JsonMediaType = "application/json"
+        protected const val FormDataMediaType = "multipart/form-data"
+        protected const val XmlMediaType = "application/xml"
 
         @JvmStatic
         val client by lazy {
@@ -26,32 +26,29 @@ open class ApiClient(val baseUrl: String) {
         val jsonHeaders: Map<String, String> = mapOf(ContentType to JsonMediaType, Accept to JsonMediaType)
     }
 
-    inline protected fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody {
-        if(content is File) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), content
-            )
-        } else if(mediaType == FormDataMediaType) {
-            var builder = FormBody.Builder()
-            // content's type *must* be Map<String, Any>
-            @Suppress("UNCHECKED_CAST")
-            (content as Map<String,String>).forEach { key, value ->
-                builder = builder.add(key, value)
-            }
-            return builder.build()
-        }  else if(mediaType == JsonMediaType) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
-            )
-        } else if (mediaType == XmlMediaType) {
-            TODO("xml not currently supported.")
-        }
-
-        // TODO: this should be extended with other serializers
-        TODO("requestBody currently only supports JSON body and File body.")
-    }
-
-    inline protected fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
+    protected inline fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody =
+         when {
+             content is File -> RequestBody.create(
+                 MediaType.parse(mediaType), content
+             )
+             mediaType == FormDataMediaType -> {
+                 var builder = FormBody.Builder()
+                 // content's type *must* be Map<String, Any>
+                 @Suppress("UNCHECKED_CAST")
+                 (content as Map<String,String>).forEach { key, value ->
+                     builder = builder.add(key, value)
+                 }
+                 builder.build()
+             }
+             mediaType == JsonMediaType -> RequestBody.create(
+                 MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
+             )
+             mediaType == XmlMediaType -> TODO("xml not currently supported.")
+             // TODO: this should be extended with other serializers
+             else -> TODO("requestBody currently only supports JSON body and File body.")
+         }
+
+    protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
         if(body == null) return null
         return when(mediaType) {
             JsonMediaType -> Serializer.moshi.adapter(T::class.java).fromJson(body.source())
@@ -59,7 +56,7 @@ open class ApiClient(val baseUrl: String) {
         }
     }
 
-    inline protected fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
+    protected inline fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
         val httpUrl = HttpUrl.parse(baseUrl) ?: throw IllegalStateException("baseUrl is invalid.")
 
         var urlBuilder = httpUrl.newBuilder()
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiInfrastructureResponse.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiInfrastructureResponse.kt.mustache
index a4e0f0f424d9..9b6bdad4ba5e 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiInfrastructureResponse.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/ApiInfrastructureResponse.kt.mustache
@@ -10,31 +10,31 @@ abstract class ApiInfrastructureResponse<T>(val responseType: ResponseType) {
 }
 
 class Success<T>(
-        val data: T,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val data: T,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiInfrastructureResponse<T>(ResponseType.Success)
 
 class Informational<T>(
-        val statusText: String,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val statusText: String,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Informational)
 
 class Redirection<T>(
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Redirection)
 
 class ClientError<T>(
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.ClientError)
 
 class ServerError<T>(
-        val message: String? = null,
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>>
+    val message: String? = null,
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>>
 ): ApiInfrastructureResponse<T>(ResponseType.ServerError)
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/RequestConfig.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/RequestConfig.kt.mustache
index 58a3d605aa11..5fc06ceb6122 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/RequestConfig.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/RequestConfig.kt.mustache
@@ -9,7 +9,8 @@ package {{packageName}}.infrastructure
  *       multi-valued headers as csv-only.
  */
 data class RequestConfig(
-        val method: RequestMethod,
-        val path: String,
-        val headers: Map<String, String> = mapOf(),
-        val query: Map<String, List<String>> = mapOf())
\ No newline at end of file
+    val method: RequestMethod,
+    val path: String,
+    val headers: Map<String, String> = mapOf(),
+    val query: Map<String, List<String>> = mapOf()
+)
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/Serializer.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/Serializer.kt.mustache
index 71cb991ddba1..9d448cb9a738 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/Serializer.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/infrastructure/Serializer.kt.mustache
@@ -8,7 +8,7 @@ import java.util.*
 object Serializer {
     @JvmStatic
     val moshi: Moshi = Moshi.Builder()
-            .add(KotlinJsonAdapterFactory())
-            .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
-            .build()
+        .add(KotlinJsonAdapterFactory())
+        .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
+        .build()
 }
diff --git a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 5c4ebd2acbce..02c7b2cddc03 100644
--- a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -5,11 +5,11 @@ import java.io.File
 
 open class ApiClient(val baseUrl: String) {
     companion object {
-        protected val ContentType = "Content-Type"
-        protected val Accept = "Accept"
-        protected val JsonMediaType = "application/json"
-        protected val FormDataMediaType = "multipart/form-data"
-        protected val XmlMediaType = "application/xml"
+        protected const val ContentType = "Content-Type"
+        protected const val Accept = "Accept"
+        protected const val JsonMediaType = "application/json"
+        protected const val FormDataMediaType = "multipart/form-data"
+        protected const val XmlMediaType = "application/xml"
 
         @JvmStatic
         val client by lazy {
@@ -26,32 +26,29 @@ open class ApiClient(val baseUrl: String) {
         val jsonHeaders: Map<String, String> = mapOf(ContentType to JsonMediaType, Accept to JsonMediaType)
     }
 
-    inline protected fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody {
-        if(content is File) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), content
-            )
-        } else if(mediaType == FormDataMediaType) {
-            var builder = FormBody.Builder()
-            // content's type *must* be Map<String, Any>
-            @Suppress("UNCHECKED_CAST")
-            (content as Map<String,String>).forEach { key, value ->
-                builder = builder.add(key, value)
-            }
-            return builder.build()
-        }  else if(mediaType == JsonMediaType) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
-            )
-        } else if (mediaType == XmlMediaType) {
-            TODO("xml not currently supported.")
-        }
-
-        // TODO: this should be extended with other serializers
-        TODO("requestBody currently only supports JSON body and File body.")
-    }
-
-    inline protected fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
+    protected inline fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody =
+         when {
+             content is File -> RequestBody.create(
+                 MediaType.parse(mediaType), content
+             )
+             mediaType == FormDataMediaType -> {
+                 var builder = FormBody.Builder()
+                 // content's type *must* be Map<String, Any>
+                 @Suppress("UNCHECKED_CAST")
+                 (content as Map<String,String>).forEach { key, value ->
+                     builder = builder.add(key, value)
+                 }
+                 builder.build()
+             }
+             mediaType == JsonMediaType -> RequestBody.create(
+                 MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
+             )
+             mediaType == XmlMediaType -> TODO("xml not currently supported.")
+             // TODO: this should be extended with other serializers
+             else -> TODO("requestBody currently only supports JSON body and File body.")
+         }
+
+    protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
         if(body == null) return null
         return when(mediaType) {
             JsonMediaType -> Serializer.moshi.adapter(T::class.java).fromJson(body.source())
@@ -59,7 +56,7 @@ open class ApiClient(val baseUrl: String) {
         }
     }
 
-    inline protected fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
+    protected inline fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
         val httpUrl = HttpUrl.parse(baseUrl) ?: throw IllegalStateException("baseUrl is invalid.")
 
         var urlBuilder = httpUrl.newBuilder()
diff --git a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
index 1f5fbf1a3f0b..f1a8aecc914b 100644
--- a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
+++ b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
@@ -10,31 +10,31 @@ abstract class ApiInfrastructureResponse<T>(val responseType: ResponseType) {
 }
 
 class Success<T>(
-        val data: T,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val data: T,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiInfrastructureResponse<T>(ResponseType.Success)
 
 class Informational<T>(
-        val statusText: String,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val statusText: String,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Informational)
 
 class Redirection<T>(
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Redirection)
 
 class ClientError<T>(
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.ClientError)
 
 class ServerError<T>(
-        val message: String? = null,
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>>
+    val message: String? = null,
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>>
 ): ApiInfrastructureResponse<T>(ResponseType.ServerError)
\ No newline at end of file
diff --git a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
index b01f63a1013a..86e2dadf9a81 100644
--- a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
+++ b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
@@ -9,7 +9,8 @@ package org.openapitools.client.infrastructure
  *       multi-valued headers as csv-only.
  */
 data class RequestConfig(
-        val method: RequestMethod,
-        val path: String,
-        val headers: Map<String, String> = mapOf(),
-        val query: Map<String, List<String>> = mapOf())
\ No newline at end of file
+    val method: RequestMethod,
+    val path: String,
+    val headers: Map<String, String> = mapOf(),
+    val query: Map<String, List<String>> = mapOf()
+)
\ No newline at end of file
diff --git a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
index 24dfb79dab1d..cf3fe8203d5b 100644
--- a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
+++ b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
@@ -8,7 +8,7 @@ import java.util.*
 object Serializer {
     @JvmStatic
     val moshi: Moshi = Moshi.Builder()
-            .add(KotlinJsonAdapterFactory())
-            .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
-            .build()
+        .add(KotlinJsonAdapterFactory())
+        .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
+        .build()
 }
diff --git a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 5c4ebd2acbce..02c7b2cddc03 100644
--- a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -5,11 +5,11 @@ import java.io.File
 
 open class ApiClient(val baseUrl: String) {
     companion object {
-        protected val ContentType = "Content-Type"
-        protected val Accept = "Accept"
-        protected val JsonMediaType = "application/json"
-        protected val FormDataMediaType = "multipart/form-data"
-        protected val XmlMediaType = "application/xml"
+        protected const val ContentType = "Content-Type"
+        protected const val Accept = "Accept"
+        protected const val JsonMediaType = "application/json"
+        protected const val FormDataMediaType = "multipart/form-data"
+        protected const val XmlMediaType = "application/xml"
 
         @JvmStatic
         val client by lazy {
@@ -26,32 +26,29 @@ open class ApiClient(val baseUrl: String) {
         val jsonHeaders: Map<String, String> = mapOf(ContentType to JsonMediaType, Accept to JsonMediaType)
     }
 
-    inline protected fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody {
-        if(content is File) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), content
-            )
-        } else if(mediaType == FormDataMediaType) {
-            var builder = FormBody.Builder()
-            // content's type *must* be Map<String, Any>
-            @Suppress("UNCHECKED_CAST")
-            (content as Map<String,String>).forEach { key, value ->
-                builder = builder.add(key, value)
-            }
-            return builder.build()
-        }  else if(mediaType == JsonMediaType) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
-            )
-        } else if (mediaType == XmlMediaType) {
-            TODO("xml not currently supported.")
-        }
-
-        // TODO: this should be extended with other serializers
-        TODO("requestBody currently only supports JSON body and File body.")
-    }
-
-    inline protected fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
+    protected inline fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody =
+         when {
+             content is File -> RequestBody.create(
+                 MediaType.parse(mediaType), content
+             )
+             mediaType == FormDataMediaType -> {
+                 var builder = FormBody.Builder()
+                 // content's type *must* be Map<String, Any>
+                 @Suppress("UNCHECKED_CAST")
+                 (content as Map<String,String>).forEach { key, value ->
+                     builder = builder.add(key, value)
+                 }
+                 builder.build()
+             }
+             mediaType == JsonMediaType -> RequestBody.create(
+                 MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
+             )
+             mediaType == XmlMediaType -> TODO("xml not currently supported.")
+             // TODO: this should be extended with other serializers
+             else -> TODO("requestBody currently only supports JSON body and File body.")
+         }
+
+    protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
         if(body == null) return null
         return when(mediaType) {
             JsonMediaType -> Serializer.moshi.adapter(T::class.java).fromJson(body.source())
@@ -59,7 +56,7 @@ open class ApiClient(val baseUrl: String) {
         }
     }
 
-    inline protected fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
+    protected inline fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
         val httpUrl = HttpUrl.parse(baseUrl) ?: throw IllegalStateException("baseUrl is invalid.")
 
         var urlBuilder = httpUrl.newBuilder()
diff --git a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
index 1f5fbf1a3f0b..f1a8aecc914b 100644
--- a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
+++ b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
@@ -10,31 +10,31 @@ abstract class ApiInfrastructureResponse<T>(val responseType: ResponseType) {
 }
 
 class Success<T>(
-        val data: T,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val data: T,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiInfrastructureResponse<T>(ResponseType.Success)
 
 class Informational<T>(
-        val statusText: String,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val statusText: String,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Informational)
 
 class Redirection<T>(
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Redirection)
 
 class ClientError<T>(
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.ClientError)
 
 class ServerError<T>(
-        val message: String? = null,
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>>
+    val message: String? = null,
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>>
 ): ApiInfrastructureResponse<T>(ResponseType.ServerError)
\ No newline at end of file
diff --git a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
index b01f63a1013a..86e2dadf9a81 100644
--- a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
+++ b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
@@ -9,7 +9,8 @@ package org.openapitools.client.infrastructure
  *       multi-valued headers as csv-only.
  */
 data class RequestConfig(
-        val method: RequestMethod,
-        val path: String,
-        val headers: Map<String, String> = mapOf(),
-        val query: Map<String, List<String>> = mapOf())
\ No newline at end of file
+    val method: RequestMethod,
+    val path: String,
+    val headers: Map<String, String> = mapOf(),
+    val query: Map<String, List<String>> = mapOf()
+)
\ No newline at end of file
diff --git a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
index 24dfb79dab1d..cf3fe8203d5b 100644
--- a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
+++ b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
@@ -8,7 +8,7 @@ import java.util.*
 object Serializer {
     @JvmStatic
     val moshi: Moshi = Moshi.Builder()
-            .add(KotlinJsonAdapterFactory())
-            .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
-            .build()
+        .add(KotlinJsonAdapterFactory())
+        .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
+        .build()
 }
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 5c4ebd2acbce..02c7b2cddc03 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -5,11 +5,11 @@ import java.io.File
 
 open class ApiClient(val baseUrl: String) {
     companion object {
-        protected val ContentType = "Content-Type"
-        protected val Accept = "Accept"
-        protected val JsonMediaType = "application/json"
-        protected val FormDataMediaType = "multipart/form-data"
-        protected val XmlMediaType = "application/xml"
+        protected const val ContentType = "Content-Type"
+        protected const val Accept = "Accept"
+        protected const val JsonMediaType = "application/json"
+        protected const val FormDataMediaType = "multipart/form-data"
+        protected const val XmlMediaType = "application/xml"
 
         @JvmStatic
         val client by lazy {
@@ -26,32 +26,29 @@ open class ApiClient(val baseUrl: String) {
         val jsonHeaders: Map<String, String> = mapOf(ContentType to JsonMediaType, Accept to JsonMediaType)
     }
 
-    inline protected fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody {
-        if(content is File) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), content
-            )
-        } else if(mediaType == FormDataMediaType) {
-            var builder = FormBody.Builder()
-            // content's type *must* be Map<String, Any>
-            @Suppress("UNCHECKED_CAST")
-            (content as Map<String,String>).forEach { key, value ->
-                builder = builder.add(key, value)
-            }
-            return builder.build()
-        }  else if(mediaType == JsonMediaType) {
-            return RequestBody.create(
-                    MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
-            )
-        } else if (mediaType == XmlMediaType) {
-            TODO("xml not currently supported.")
-        }
-
-        // TODO: this should be extended with other serializers
-        TODO("requestBody currently only supports JSON body and File body.")
-    }
-
-    inline protected fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
+    protected inline fun <reified T> requestBody(content: T, mediaType: String = JsonMediaType): RequestBody =
+         when {
+             content is File -> RequestBody.create(
+                 MediaType.parse(mediaType), content
+             )
+             mediaType == FormDataMediaType -> {
+                 var builder = FormBody.Builder()
+                 // content's type *must* be Map<String, Any>
+                 @Suppress("UNCHECKED_CAST")
+                 (content as Map<String,String>).forEach { key, value ->
+                     builder = builder.add(key, value)
+                 }
+                 builder.build()
+             }
+             mediaType == JsonMediaType -> RequestBody.create(
+                 MediaType.parse(mediaType), Serializer.moshi.adapter(T::class.java).toJson(content)
+             )
+             mediaType == XmlMediaType -> TODO("xml not currently supported.")
+             // TODO: this should be extended with other serializers
+             else -> TODO("requestBody currently only supports JSON body and File body.")
+         }
+
+    protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String = JsonMediaType): T? {
         if(body == null) return null
         return when(mediaType) {
             JsonMediaType -> Serializer.moshi.adapter(T::class.java).fromJson(body.source())
@@ -59,7 +56,7 @@ open class ApiClient(val baseUrl: String) {
         }
     }
 
-    inline protected fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
+    protected inline fun <reified T: Any?> request(requestConfig: RequestConfig, body : Any? = null): ApiInfrastructureResponse<T?> {
         val httpUrl = HttpUrl.parse(baseUrl) ?: throw IllegalStateException("baseUrl is invalid.")
 
         var urlBuilder = httpUrl.newBuilder()
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
index 1f5fbf1a3f0b..f1a8aecc914b 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiInfrastructureResponse.kt
@@ -10,31 +10,31 @@ abstract class ApiInfrastructureResponse<T>(val responseType: ResponseType) {
 }
 
 class Success<T>(
-        val data: T,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val data: T,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiInfrastructureResponse<T>(ResponseType.Success)
 
 class Informational<T>(
-        val statusText: String,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val statusText: String,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Informational)
 
 class Redirection<T>(
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.Redirection)
 
 class ClientError<T>(
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>> = mapOf()
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
 ) : ApiInfrastructureResponse<T>(ResponseType.ClientError)
 
 class ServerError<T>(
-        val message: String? = null,
-        val body: Any? = null,
-        override val statusCode: Int = -1,
-        override val headers: Map<String, List<String>>
+    val message: String? = null,
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>>
 ): ApiInfrastructureResponse<T>(ResponseType.ServerError)
\ No newline at end of file
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
index b01f63a1013a..86e2dadf9a81 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
@@ -9,7 +9,8 @@ package org.openapitools.client.infrastructure
  *       multi-valued headers as csv-only.
  */
 data class RequestConfig(
-        val method: RequestMethod,
-        val path: String,
-        val headers: Map<String, String> = mapOf(),
-        val query: Map<String, List<String>> = mapOf())
\ No newline at end of file
+    val method: RequestMethod,
+    val path: String,
+    val headers: Map<String, String> = mapOf(),
+    val query: Map<String, List<String>> = mapOf()
+)
\ No newline at end of file
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
index 24dfb79dab1d..cf3fe8203d5b 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
@@ -8,7 +8,7 @@ import java.util.*
 object Serializer {
     @JvmStatic
     val moshi: Moshi = Moshi.Builder()
-            .add(KotlinJsonAdapterFactory())
-            .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
-            .build()
+        .add(KotlinJsonAdapterFactory())
+        .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
+        .build()
 }
diff --git a/samples/server/petstore/kotlin-server/ktor/.openapi-generator/VERSION b/samples/server/petstore/kotlin-server/ktor/.openapi-generator/VERSION
index 1c00c5181548..0628777500bd 100644
--- a/samples/server/petstore/kotlin-server/ktor/.openapi-generator/VERSION
+++ b/samples/server/petstore/kotlin-server/ktor/.openapi-generator/VERSION
@@ -1 +1 @@
-3.0.2-SNAPSHOT
\ No newline at end of file
+3.1.0-SNAPSHOT
\ No newline at end of file
diff --git a/samples/server/petstore/kotlin-server/ktor/README.md b/samples/server/petstore/kotlin-server/ktor/README.md
index a2d2c5e11ab8..82c3596aa35a 100644
--- a/samples/server/petstore/kotlin-server/ktor/README.md
+++ b/samples/server/petstore/kotlin-server/ktor/README.md
@@ -2,7 +2,7 @@
 
 This is a sample server Petstore server. For this sample, you can use the api key &#x60;special-key&#x60; to test the authorization filters.
 
-Generated by OpenAPI Generator 3.0.2-SNAPSHOT.
+Generated by OpenAPI Generator 3.1.0-SNAPSHOT.
 
 ## Requires