support run HTTP server with specific net.Listener (#2023)

gin.go

@@ -338,6 +338,15 @@ func (engine *Engine) RunFd(fd int) (err error) {
 		return
 	}
 	defer listener.Close()
+	err = engine.RunListener(listener)
+	return
+}
+
+// RunListener attaches the router to a http.Server and starts listening and serving HTTP requests
+// through the specified net.Listener
+func (engine *Engine) RunListener(listener net.Listener) (err error) {
+	debugPrint("Listening and serving HTTP on listener what's bind with address@%s", listener.Addr())
+	defer func() { debugPrintError(err) }()
 	err = http.Serve(listener, engine)
 	return
 }