code: func (s HashExpireyStrategy) Expired(location string,
  	pool *redis.Pool) (expired []string, err error) {
  
  	now := time.Now().UTC()
  
  	cnx := pool.Get()
  	defer cnx.Close()
  
  	reply, err := redis.StringMap(cnx.Do("HGETALL", location))
  	if err != nil {
  		return
  	}
  
  	for id, tick := range reply {
  		lastUpdate, err := time.Parse(DefaultTimeFormat, tick)
  
  		if err != nil {
  			continue
  		} else if lastUpdate.Add(s.MaxAge).Before(now) {
  			expired = append(expired, id)
  		}
  	}
  
  	return
  }
docs: // Expired implements the `func Expired` defined on the Strategy interface. It
  // scans iteratively over the Heart's `location` field to look for items that
  // have expired. An item is marked as expired iff the last update time happened
  // before the instant of the maxAge subtracted from the current time.