fix: Conform to go test naming convention

As reported in #835 go vet reporting the violation of
naming convention of go test.
see: https://pkg.go.dev/testing#hdr-Examples

Although this project use golangci-lint as linter and
it has functionality to skip by nolint:govet, so basically
there is no problems.
However if there is no cons, it is better to conform with
naming convention and fix the code like below.
https://github.com/golang-migrate/migrate/blob/c367ed2f12b8549c2ace442c440a9e312348951d/dktesting/example_test.go#L17

testing/testing_test.go

@@ -4,7 +4,9 @@ import (
 	"testing"
 )
 
-func ExampleParallelTest(t *testing.T) { // nolint:govet
+func ExampleParallelTest() {
+	t := &testing.T{} // Should actually be used in a Test
+
 	var isReady = func(i Instance) bool {
 		// Return true if Instance is ready to run tests.
 		// Don't block here though.