На примере Gorilla Websocket CloseGoingAway

r.GET("/ws", func(c *gin.Context) {
	ws, err := socketUpgrade.Upgrade(c.Writer, c.Request, nil)
	defer ws.Close()
 
	var data struct {
		A string `json:"a"`
		B int    `json:"b"`
	}
 
	count := 0
	for {
		err = ws.ReadJSON(&data)
		if err != nil {
			if closeErr, ok := err.(*websocket.CloseError); ok && closeErr.Code == websocket.CloseGoingAway {
				log.Println("ws_client disconnected")
				return
			}
			assert(err)
		}
		count += 1
		err = ws.WriteJSON(gin.H{
			"a": data.A,
			"b": data.B,
			"c": count,
		})
		if err != nil {
			if closeErr, ok := err.(*websocket.CloseError); ok && closeErr.Code == websocket.CloseGoingAway {
				log.Println("ws_client disconnected")
				return
			}
			assert(err)
		}
	}
})