code: func (w *watchQueue) Enqueue(key string, kvp *kvdb.KVPair, err error) {
  	w.m.Lock()
  	w.updates.PushBack(&watchUpdate{key: key, kvp: kvp, err: err})
  	w.cv.Signal()
  	w.m.Unlock()
  }
docs: // Enqueue enqueues and never blocks