code: public static void sendClose(final CloseMessage closeMessage, final WebSocketChannel wsChannel, final WebSocketCallback<Void> callback) {
          sendClose(closeMessage, wsChannel, callback, null);
      }
docs: Sends a complete close message, invoking the callback when complete
  
  @param closeMessage The close message
  @param wsChannel The web socket channel
  @param callback The callback to invoke on completion