docs: @Controller(events = EventType.MESSAGE, pattern = "^([a-z ]{2})(\\d+)([a-z ]{2})$")
      public void onReceiveMessage(WebSocketSession session, Event event, Matcher matcher) {
          reply(session, event, "First group: " + matcher.group(0) + "\n" +
                  "Second group: " + matcher.group(1) + "\n" +
                  "Third group: " + matcher.group(2) + "\n" +
                  "Fourth group: " + matcher.group(3));
      }