code: func (ps *peerSet) Unregister(id string) error {
  	ps.lock.Lock()
  	p, ok := ps.peers[id]
  	if !ok {
  		defer ps.lock.Unlock()
  		return errNotRegistered
  	}
  	delete(ps.peers, id)
  	ps.lock.Unlock()
  
  	ps.peerDropFeed.Send(p)
  	return nil
  }
docs: // Unregister removes a remote peer from the active set, disabling any further
  // actions to/from that particular entity.