code: func (i *itemWithExp) isAcceptableTTL(now time.Time, minTTL time.Duration) bool {
  	if i.exp.IsZero() {
  		return true // never expires
  	}
  	// Note: '>=' must not be used here, since minTTL may be 0, and we don't want
  	// to return true on zero expiration.
  	return i.exp.Sub(now) > minTTL
  }
docs: // isAcceptableTTL returns true if item's TTL is large enough.