code: func (mem *Memcache) Set(key string, val interface{}, timeout time.Duration) (err error) {
  	var data []byte
  	if data, err = json.Marshal(val); err != nil {
  		return err
  	}
  
  	item := &memcache.Item{Key: key, Value: data, Expiration: int32(timeout / time.Second)}
  	return mem.conn.Set(item)
  }
docs: //Set cached value with key and expire time.