fix: resolve concurrent write crash on gorilla/websocket by adding wsWriteMu mutex

client/app.go

@@ -140,6 +140,7 @@ type App struct {
 	chatUnread        int
 	replyStaffID      uint
 	fetchAppsMu       sync.Mutex
+	wsWriteMu         sync.Mutex
 }
 
 type LocalStats struct {
@@ -608,23 +609,32 @@ func (a *App) GetStats() map[string]any {
 	}
 }
 
+// safeWriteWS writes a message to the WebSocket connection thread-safely
+func (a *App) safeWriteWS(msg any) error {
+	a.mu.Lock()
+	conn := a.wsConn
+	a.mu.Unlock()
+
+	if conn == nil {
+		return errors.New("websocket connection is nil")
+	}
+
+	a.wsWriteMu.Lock()
+	defer a.wsWriteMu.Unlock()
+	return conn.WriteJSON(msg)
+}
+
 // SendWebcamFrame truyền webcam frame từ JS frontend lên máy chủ qua WS
 func (a *App) SendWebcamFrame(frameBase64 string) {
 	if !a.isMonitoringActive() {
 		return
 	}
-	a.mu.Lock()
-	conn := a.wsConn
-	a.mu.Unlock()
-
-	if conn != nil {
-		_ = conn.WriteJSON(map[string]any{
-			"event": "webcam_stream_frame",
-			"data": map[string]any{
-				"imageBuffer": frameBase64,
-			},
-		})
-	}
+	_ = a.safeWriteWS(map[string]any{
+		"event": "webcam_stream_frame",
+		"data": map[string]any{
+			"imageBuffer": frameBase64,
+		},
+	})
 }
 
 // authStorageScanner chỉ quét localStorage khi người dùng chủ động mở trang đăng nhập
@@ -1225,18 +1235,12 @@ func (a *App) startScreenshotStream() {
 					continue
 				}
 
-				a.mu.Lock()
-				conn := a.wsConn
-				a.mu.Unlock()
-
-				if conn != nil {
-					_ = conn.WriteJSON(map[string]any{
-						"event": "screenshot_stream_frame",
-						"data": map[string]any{
-							"imageBuffer": frame,
-						},
-					})
-				}
+				_ = a.safeWriteWS(map[string]any{
+					"event": "screenshot_stream_frame",
+					"data": map[string]any{
+						"imageBuffer": frame,
+					},
+				})
 			case <-a.streamScStop:
 				return
 			}
@@ -1301,22 +1305,14 @@ func (a *App) startWebcamStream() {
 				emptyCount = 0
 				sentCount++
 
-				a.mu.Lock()
-				conn := a.wsConn
-				a.mu.Unlock()
-
-				if conn != nil {
-					err := conn.WriteJSON(map[string]any{
-						"event": "webcam_stream_frame",
-						"data": map[string]any{
-							"imageBuffer": frame,
-						},
-					})
-					if sentCount <= 5 {
-						log.Printf("[WS] Webcam frame #%d sent (len=%d, err=%v)", sentCount, len(frame), err)
-					}
-				} else if sentCount <= 5 {
-					log.Printf("[WS] Webcam frame #%d: no WS connection", sentCount)
+				err := a.safeWriteWS(map[string]any{
+					"event": "webcam_stream_frame",
+					"data": map[string]any{
+						"imageBuffer": frame,
+					},
+				})
+				if sentCount <= 5 {
+					log.Printf("[WS] Webcam frame #%d sent (len=%d, err=%v)", sentCount, len(frame), err)
 				}
 			case <-a.streamCamStop:
 				return