Detach asynchronous request from current context

httpcache.go

@@ -8,6 +8,7 @@ package httpcache
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"errors"
 	"io"
 	"io/ioutil"
@@ -171,11 +172,10 @@ func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error
 			if freshness == fresh {
 				return cachedResp, nil
 			} else if freshness == staleWhileRevalidate {
-				noCacheRequest := *req
-				noCacheRequest.Header = noCacheRequest.Header.Clone()
+				noCacheRequest := req.Clone(context.Background()) // Is this the right thing?
 				noCacheRequest.Header.Set("cache-control", "no-cache")
 				go func() {
-					resp, err := t.RoundTrip(&noCacheRequest)
+					resp, err := t.RoundTrip(noCacheRequest)
 					if err == nil {
 						defer resp.Body.Close()
 						buffer := make([]byte, 4096)