code: func (t *MockTransport) WriteTo(b []byte, addr string) (time.Time, error) {
  	dest, ok := t.net.transports[addr]
  	if !ok {
  		return time.Time{}, fmt.Errorf("No route to %q", addr)
  	}
  
  	now := time.Now()
  	dest.packetCh <- &Packet{
  		Buf:       b,
  		From:      t.addr,
  		Timestamp: now,
  	}
  	return now, nil
  }
docs: // See Transport.