code: func (auth *AuthProxy) Remember() *Error {
  
  	// Make sure we do not rewrite the expiration time
  	if auth.InCache() {
  		return nil
  	}
  
  	var (
  		key        = auth.getKey()
  		value, _   = auth.GetUserIDViaCache()
  		expiration = time.Duration(-auth.cacheTTL) * time.Minute
  
  		err = auth.store.Set(key, value, expiration)
  	)
  
  	if err != nil {
  		return newError(err.Error(), nil)
  	}
  
  	return nil
  }
docs: // Remember user in cache