code: func (eps *transportEndpoints) unregisterEndpoint(id TransportEndpointID, ep TransportEndpoint) {
  	eps.mu.Lock()
  	defer eps.mu.Unlock()
  	e, ok := eps.endpoints[id]
  	if !ok {
  		return
  	}
  	if multiPortEp, ok := e.(*multiPortEndpoint); ok {
  		if !multiPortEp.unregisterEndpoint(ep) {
  			return
  		}
  	}
  	delete(eps.endpoints, id)
  }
docs: // unregisterEndpoint unregisters the endpoint with the given id such that it
  // won't receive any more packets.