rpc: exit from Start after Listener is running

If port is dynamically allocated, `(*Server).Addr` will contain
0 port. This commit executes listener before exiting from `Start()`
and sets Addr to the actual address.

cli/server/server.go

@@ -355,7 +355,7 @@ func startServer(ctx *cli.Context) error {
 	errChan := make(chan error)
 
 	go serv.Start(errChan)
-	go rpcServer.Start(errChan)
+	rpcServer.Start(errChan)
 
 	fmt.Fprintln(ctx.App.Writer, logo())
 	fmt.Fprintln(ctx.App.Writer, serv.UserAgent)

pkg/rpc/server/server.go

@@ -167,18 +167,32 @@ func (s *Server) Start(errChan chan error) {
 		s.https.Handler = http.HandlerFunc(s.handleHTTPRequest)
 		s.log.Info("starting rpc-server (https)", zap.String("endpoint", s.https.Addr))
 		go func() {
-			err := s.https.ListenAndServeTLS(cfg.CertFile, cfg.KeyFile)
+			ln, err := net.Listen("tcp", s.https.Addr)
+			if err != nil {
+				errChan <- err
+				return
+			}
+			s.https.Addr = ln.Addr().String()
+			err = s.https.ServeTLS(ln, cfg.CertFile, cfg.KeyFile)
 			if err != http.ErrServerClosed {
 				s.log.Error("failed to start TLS RPC server", zap.Error(err))
 				errChan <- err
 			}
 		}()
 	}
-	err := s.ListenAndServe()
+	ln, err := net.Listen("tcp", s.Addr)
-	if err != http.ErrServerClosed {
+	if err != nil {
-		s.log.Error("failed to start RPC server", zap.Error(err))
 		errChan <- err
+		return
 	}
+	s.Addr = ln.Addr().String() // set Addr to the actual address
+	go func() {
+		err = s.Serve(ln)
+		if err != http.ErrServerClosed {
+			s.log.Error("failed to start RPC server", zap.Error(err))
+			errChan <- err
+		}
+	}()
 }
 
 // Shutdown overrides the http.Server Shutdown

pkg/rpc/server/server_helper_test.go

@@ -68,7 +68,7 @@ func initClearServerWithInMemoryChain(t *testing.T) (*core.Blockchain, *Server,
 	require.NoError(t, err)
 	rpcServer := New(chain, cfg.ApplicationConfiguration.RPC, server, logger)
 	errCh := make(chan error, 2)
-	go rpcServer.Start(errCh)
+	rpcServer.Start(errCh)
 
 	handler := http.HandlerFunc(rpcServer.handleHTTPRequest)
 	srv := httptest.NewServer(handler)