code: func (kv *consulKV) getActiveSession(key string) (string, error) {
  	pair, _, err := kv.client.Get(key, nil)
  	if err != nil {
  		return "", err
  	}
  	if pair != nil && pair.Session != "" {
  		return pair.Session, nil
  	}
  	return "", nil
  }
docs: // getActiveSession checks if the key already has
  // a session attached