code: func (nc *Conn) respHandler(m *Msg) {
  	rt := respToken(m.Subject)
  
  	nc.mu.Lock()
  	// Just return if closed.
  	if nc.isClosed() {
  		nc.mu.Unlock()
  		return
  	}
  
  	// Grab mch
  	mch := nc.respMap[rt]
  	// Delete the key regardless, one response only.
  	// FIXME(dlc) - should we track responses past 1
  	// just statistics wise?
  	delete(nc.respMap, rt)
  	nc.mu.Unlock()
  
  	// Don't block, let Request timeout instead, mch is
  	// buffered and we should delete the key before a
  	// second response is processed.
  	select {
  	case mch <- m:
  	default:
  		return
  	}
  }
docs: // respHandler is the global response handler. It will look up
  // the appropriate channel based on the last token and place
  // the message on the channel if possible.