added a notify system

hws/responsewriter.go

@@ -13,3 +13,7 @@ func (w *wrappedWriter) WriteHeader(statusCode int) {
 	w.ResponseWriter.WriteHeader(statusCode)
 	w.statusCode = statusCode
 }
+
+func (w *wrappedWriter) Unwrap() http.ResponseWriter {
+	return w.ResponseWriter
+}