code: function _closeOnSignal(signal) {
      process.on(signal, onSignal);
  
      /**
       * @returns {void}
       */
      function onSignal() {
        logger.info({ workerName: configuration.workerName, signal },
          '[worker#listen] Received exit signal, stopping workers...');
        workers.close(true);
      }
    }
docs: Listen to exit signal such as SIGINT and close the workers
  @param {String} signal name (e.g. SIGINT)
  @returns {void}
  @private