Add Unwrap method to http.ResponseWriter implementations. (#283)

Also update httpsnoop to version 1.0.3, which supports Unwrap method as well.

middleware/errorhandler.go

@@ -51,6 +51,11 @@ func newErrorInterceptor(w http.ResponseWriter, code int) *errorInterceptor {
 	return &i
 }
 
+// Unwrap method is used by http.ResponseController to get access to original http.ResponseWriter.
+func (i *errorInterceptor) Unwrap() http.ResponseWriter {
+	return i.originalWriter
+}
+
 // Header implements http.ResponseWriter
 func (i *errorInterceptor) Header() http.Header {
 	return i.headers

middleware/response.go

@@ -52,6 +52,11 @@ func newBadResponseLoggingWriter(rw http.ResponseWriter, buffer io.Writer) badRe
 	return &b
 }
 
+// Unwrap method is used by http.ResponseController to get access to original http.ResponseWriter.
+func (b *nonFlushingBadResponseLoggingWriter) Unwrap() http.ResponseWriter {
+	return b.rw
+}
+
 // Header returns the header map that will be sent by WriteHeader.
 // Implements ResponseWriter.
 func (b *nonFlushingBadResponseLoggingWriter) Header() http.Header {

middleware/response_test.go

@@ -78,3 +78,13 @@ func TestBadResponseLoggingWriter_WithAndWithoutFlusher(t *testing.T) {
 		t.Errorf("Flush should have worked but did not")
 	}
 }
+
+type responseWriterWithUnwrap interface {
+	http.ResponseWriter
+	Unwrap() http.ResponseWriter
+}
+
+// Verify that custom http.ResponseWriter implementations implement Unwrap() method, used by http.ResponseContoller.
+var _ responseWriterWithUnwrap = &nonFlushingBadResponseLoggingWriter{}
+var _ responseWriterWithUnwrap = &flushingBadResponseLoggingWriter{}
+var _ responseWriterWithUnwrap = &errorInterceptor{}