code: public static synchronized void websocket(String url, BiConsumer<WebSocketChannel, BufferedTextMessage> onMessage) {
          checkStarted();
          instance().endpoints.add(HandlerUtil.websocket(url, new WebsocketEndpoint() {
              @Override
              public void onConnect(WebSocketHttpExchange exchange, WebSocketChannel channel) {
  
              }
  
              @Override
              protected void onFullTextMessage(WebSocketChannel channel, BufferedTextMessage message) throws IOException {
                  onMessage.accept(channel, message);
              }
          }));
      }
docs: A simplified Websocket endpoint. Supports path variables
  
  @param url       The relative URL to be map this endpoint.
  @param onMessage The handler for when a new message is received