CloseNotifier: return pointer instead of value

pkg/middlewares/metrics/metrics_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/go-kit/kit/metrics"
+	"github.com/stretchr/testify/assert"
 )
 
 // CollectingCounter is a metrics.Counter implementation that enables access to the CounterValue and LastLabelValues.
@@ -56,3 +57,44 @@ func newCollectingRetryMetrics() *collectingRetryMetrics {
 func (m *collectingRetryMetrics) ServiceRetriesCounter() metrics.Counter {
 	return m.retriesCounter
 }
+
+type rwWithCloseNotify struct {
+	*httptest.ResponseRecorder
+}
+
+func (r *rwWithCloseNotify) CloseNotify() <-chan bool {
+	panic("implement me")
+}
+
+func TestCloseNotifier(t *testing.T) {
+	testCases := []struct {
+		rw                      http.ResponseWriter
+		desc                    string
+		implementsCloseNotifier bool
+	}{
+		{
+			rw:                      httptest.NewRecorder(),
+			desc:                    "does not implement CloseNotifier",
+			implementsCloseNotifier: false,
+		},
+		{
+			rw:                      &rwWithCloseNotify{httptest.NewRecorder()},
+			desc:                    "implements CloseNotifier",
+			implementsCloseNotifier: true,
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			_, ok := test.rw.(http.CloseNotifier)
+			assert.Equal(t, test.implementsCloseNotifier, ok)
+
+			rw := newResponseRecorder(test.rw)
+			_, impl := rw.(http.CloseNotifier)
+			assert.Equal(t, test.implementsCloseNotifier, impl)
+		})
+	}
+}

pkg/middlewares/metrics/recorder.go

@@ -20,7 +20,7 @@ func newResponseRecorder(rw http.ResponseWriter) recorder {
 	if _, ok := rw.(http.CloseNotifier); !ok {
 		return rec
 	}
-	return responseRecorderWithCloseNotify{rec}
+	return &responseRecorderWithCloseNotify{rec}
 }
 
 // responseRecorder captures information from the response and preserves it for
@@ -55,13 +55,6 @@ func (r *responseRecorder) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	return r.ResponseWriter.(http.Hijacker).Hijack()
 }
 
-// CloseNotify returns a channel that receives at most a
-// single value (true) when the client connection has gone
-// away.
-func (r *responseRecorder) CloseNotify() <-chan bool {
-	return r.ResponseWriter.(http.CloseNotifier).CloseNotify()
-}
-
 // Flush sends any buffered data to the client.
 func (r *responseRecorder) Flush() {
 	if f, ok := r.ResponseWriter.(http.Flusher); ok {