code: func (ctrl *PersistentVolumeController) enqueueWork(queue workqueue.Interface, obj interface{}) {
  	// Beware of "xxx deleted" events
  	if unknown, ok := obj.(cache.DeletedFinalStateUnknown); ok && unknown.Obj != nil {
  		obj = unknown.Obj
  	}
  	objName, err := controller.KeyFunc(obj)
  	if err != nil {
  		klog.Errorf("failed to get key from object: %v", err)
  		return
  	}
  	klog.V(5).Infof("enqueued %q for sync", objName)
  	queue.Add(objName)
  }
docs: // enqueueWork adds volume or claim to given work queue.