code: public static String addSession(String message, IoSession session) {
          return format("[%s] %s", getId(session), message);
      }
docs: Prepends short session details (result of getId) for the session in square brackets to the message.
  @param message   the message to be logged
  @param session   an instance of IoSessionEx
  @return example: "[wsn#34 127.0.0.0.1:41234] this is the log message"