docs: function stopWorker(worker){
      return new Promise(function(resolve, reject){
          // set kill timeout
          const killTimeout = setTimeout(() => {
              // kill the worker
              worker.kill();
              
              // failed to disconnect within given time
              reject(new Error(`process ${worker.process.pid} killed by timeout of ${_workerShutdownTimeout/1000}s - disconnect() failed`));
          }, _workerShutdownTimeout);
  
          // wait for exit + disconnect
          worker.on('disconnect', () => {
              _logger.log(`disconnect event ${worker.process.pid}`);
              // disable kill timer
              clearTimeout(killTimeout);
  
              // ok
              resolve();
          });
  
          // trigger disconnect
          worker.disconnect();
      });
  }