code: func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
  	items := make(map[string]Item)
  	return newCacheWithJanitor(defaultExpiration, cleanupInterval, items)
  }
docs: // Return a new cache with a given default expiration duration and cleanup
  // interval. If the expiration duration is less than one (or NoExpiration),
  // the items in the cache never expire (by default), and must be deleted
  // manually. If the cleanup interval is less than one, expired items are not
  // deleted from the cache before calling c.DeleteExpired().