code: public static <T> void sendClose(final CloseMessage closeMessage, final WebSocketChannel wsChannel, final WebSocketCallback<T> callback, T context) {
          wsChannel.setCloseCode(closeMessage.getCode());
          wsChannel.setCloseReason(closeMessage.getReason());
          sendInternal(closeMessage.toByteBuffer(), WebSocketFrameType.CLOSE, wsChannel, callback, context, -1);
      }
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
  @param context The context object that will be passed to the callback on completion