code: func (k *Kademlia) NeighbourhoodDepthC() <-chan int {
  	k.lock.Lock()
  	defer k.lock.Unlock()
  	if k.nDepthC == nil {
  		k.nDepthC = make(chan int)
  	}
  	return k.nDepthC
  }
docs: // NeighbourhoodDepthC returns the channel that sends a new kademlia
  // neighbourhood depth on each change.
  // Not receiving from the returned channel will block On function
  // when the neighbourhood depth is changed.
  // TODO: Why is this exported, and if it should be; why can't we have more subscribers than one?