refine warden server start

pkg/net/rpc/warden/server.go

@@ -302,17 +302,10 @@ func (s *Server) RunUnix(file string) error {
 // will panic if any error happend
 // return server itself
 func (s *Server) Start() (*Server, error) {
-	lis, err := net.Listen(s.conf.Network, s.conf.Addr)
+	_, err := s.startWithAddr()
 	if err != nil {
 		return nil, err
 	}
-	log.Info("warden: start grpc listen addr: %v", lis.Addr())
-	reflection.Register(s.server)
-	go func() {
-		if err := s.Serve(lis); err != nil {
-			panic(err)
-		}
-	}()
 	return s, nil
 }
 
@@ -321,10 +314,18 @@ func (s *Server) Start() (*Server, error) {
 // return server itself and the actually listened address (if configured listen
 // port is zero, the os will allocate an unused port)
 func (s *Server) StartWithAddr() (*Server, net.Addr, error) {
-	lis, err := net.Listen(s.conf.Network, s.conf.Addr)
+	addr, err := s.startWithAddr()
 	if err != nil {
 		return nil, nil, err
 	}
+	return s, addr, nil
+}
+
+func (s *Server) startWithAddr() (net.Addr, error) {
+	lis, err := net.Listen(s.conf.Network, s.conf.Addr)
+	if err != nil {
+		return nil, err
+	}
 	log.Info("warden: start grpc listen addr: %v", lis.Addr())
 	reflection.Register(s.server)
 	go func() {
@@ -332,7 +333,7 @@ func (s *Server) StartWithAddr() (*Server, net.Addr, error) {
 			panic(err)
 		}
 	}()
-	return s, lis.Addr(), nil
+	return lis.Addr(), nil
 }
 
 // Serve accepts incoming connections on the listener lis, creating a new