code: func (s *Settings) CacheExpiration() time.Duration {
  	if s.CacheExpirationSec > 0 {
  		return time.Second * time.Duration(s.CacheExpirationSec)
  	}
  	return 0
  }
docs: // CacheExpiration returns a Duration representing the configured cache
  // expiration. If the cache expiration is not configured, CacheExpiration
  // will return 0.