add close flag into wsConnection to avoid duplicate calls of CloseFunc

graphql/handler/transport/websocket.go

@@ -40,6 +40,7 @@ type (
 		keepAliveTicker *time.Ticker
 		pingPongTicker  *time.Ticker
 		exec            graphql.GraphExecutor
+		closed          bool
 
 		initPayload InitPayload
 	}
@@ -441,10 +442,15 @@ func (c *wsConnection) sendConnectionError(format string, args ...interface{}) {
 
 func (c *wsConnection) close(closeCode int, message string) {
 	c.mu.Lock()
+	if c.closed {
+		c.mu.Unlock()
+		return
+	}
 	_ = c.conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(closeCode, message))
 	for _, closer := range c.active {
 		closer()
 	}
+	c.closed = true
 	c.mu.Unlock()
 	_ = c.conn.Close()
 

graphql/handler/transport/websocket_test.go

@@ -500,6 +500,39 @@ func TestWebSocketCloseFunc(t *testing.T) {
 		}
 	})
 
+	t.Run("the on close handler gets called only once when the websocket is closed", func(t *testing.T) {
+		closeFuncCalled := make(chan bool, 1)
+		h := testserver.New()
+		h.AddTransport(transport.Websocket{
+			CloseFunc: func(_ context.Context, _closeCode int) {
+				closeFuncCalled <- true
+			},
+		})
+
+		srv := httptest.NewServer(h)
+		defer srv.Close()
+
+		c := wsConnect(srv.URL)
+		require.NoError(t, c.WriteJSON(&operationMessage{Type: connectionInitMsg}))
+		assert.Equal(t, connectionAckMsg, readOp(c).Type)
+		assert.Equal(t, connectionKeepAliveMsg, readOp(c).Type)
+		require.NoError(t, c.WriteJSON(&operationMessage{Type: connectionTerminateMsg}))
+
+		select {
+		case res := <-closeFuncCalled:
+			assert.True(t, res)
+		case <-time.NewTimer(time.Millisecond * 20).C:
+			assert.Fail(t, "The close handler was not called in time")
+		}
+
+		select {
+		case <-closeFuncCalled:
+			assert.Fail(t, "The close handler was called more than once")
+		case <-time.NewTimer(time.Millisecond * 20).C:
+			// ok
+		}
+	})
+
 	t.Run("init func errors call the close handler", func(t *testing.T) {
 		h := testserver.New()
 		closeFuncCalled := make(chan bool, 1)