code: func (mkc *memoryKeyCacher) handleOverflow() {
  	if mkc.maxCacheSize < len(mkc.entries) {
  		var oldestEntryKeyID string
  		var latestAddedTime = time.Now()
  		for entryKeyID, entry := range mkc.entries {
  			if entry.addedAt.Before(latestAddedTime) {
  				latestAddedTime = entry.addedAt
  				oldestEntryKeyID = entryKeyID
  			}
  		}
  		delete(mkc.entries, oldestEntryKeyID)
  	}
  }
docs: // handleOverflow deletes the oldest key from the cache if overflowed