code: func (p *pool) Get(joinEUI lorawan.EUI64) (Client, error) {
  	if !p.resolveJoinEUI {
  		return p.defaultClient, nil
  	}
  
  	p.RLock()
  	pc, ok := p.clients[joinEUI]
  	p.RUnlock()
  	if ok {
  		return pc.client, nil
  	}
  
  	client, err := p.resolveJoinServer(joinEUI)
  	if err != nil {
  		log.WithField("join_eui", joinEUI).WithError(err).Warning("resolving JoinEUI failed, using default join-server")
  		return p.defaultClient, nil
  	}
  
  	p.Lock()
  	p.clients[joinEUI] = poolClient{client: client}
  	p.Unlock()
  
  	return client, nil
  }
docs: // Get returns the join-server client for the given joinEUI.