code: public function receiveMessage(&$worker)
      {
          $workers = $this->workers;
          Selectable::selectRead($workers, null);
          if (!count($workers)) {
              throw new Exception\RuntimeException('selectRead returned an empty array (this should not happen)');
          }
          $worker = reset($workers);
  
          return $worker->receiveMessage();
      }
docs: @param Worker $worker
  
  @throws Exception\RuntimeException
  
  @return mixed