code: func (c *Context) UpdateServiceCache(key string, update interface{}, res interface{}) error {
  
  	exists := c.updateCacheVal("service", key, update, res)
  
  	if !exists {
  		log.WithField("key", key).Error("Can't update sevices cache value")
  	}
  	return nil
  }
docs: // UpdateServiceCache updates the Services's cache using MongoDB Update query (see trello service as example)