code: func (w *WebsocketSession) Send(str string) error {
  	if atomic.LoadInt32(&w.closed) == 1 {
  		return ErrSessionClosed
  	}
  
  	w.mu.Lock()
  	defer w.mu.Unlock()
  
  	b, _ := json.Marshal([]string{str})
  	return w.conn.WriteMessage(websocket.TextMessage, b)
  }
docs: // Send sends one text frame to session