code: func (k *Kademlia) CloseNeighbourhoodDepthC() {
  	k.lock.Lock()
  	defer k.lock.Unlock()
  
  	if k.nDepthC != nil {
  		close(k.nDepthC)
  		k.nDepthC = nil
  	}
  }
docs: // CloseNeighbourhoodDepthC closes the channel returned by
  // NeighbourhoodDepthC and stops sending neighbourhood change.