[#60] Implement flusher on all http.ResponseWriters

Signed-off-by: Alex Vanin <a.vanin@yadro.com>

api/metrics.go

@@ -286,6 +286,12 @@ func (w *responseWrapper) Flush() {
 	}
 }
 
+func (w *writeCounter) Flush() {
+	if f, ok := w.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
 func (w *writeCounter) Write(p []byte) (int, error) {
 	n, err := w.ResponseWriter.Write(p)
 	atomic.AddUint64(&w.countBytes, uint64(n))

api/router.go

@@ -117,6 +117,12 @@ func (lrw *logResponseWriter) WriteHeader(code int) {
 	})
 }
 
+func (lrw *logResponseWriter) Flush() {
+	if f, ok := lrw.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
 func setRequestID(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		// generate random UUIDv4