code: func (b *ETCDBindingStorage) GetUserFrontendID(uid, frontendType string) (string, error) {
  	etcdRes, err := b.cli.Get(context.Background(), getUserBindingKey(uid, frontendType))
  	if err != nil {
  		return "", err
  	}
  	if len(etcdRes.Kvs) == 0 {
  		return "", constants.ErrBindingNotFound
  	}
  	return string(etcdRes.Kvs[0].Value), nil
  }
docs: // GetUserFrontendID gets the id of the frontend server a user is connected to
  // TODO: should we set context here?
  // TODO: this could be way more optimized, using watcher and local caching