func NewCache(d time.Duration) *Cache {
	return &Cache{
		values:   make(map[string]*cacheItem),
		lifetime: d,
	}
}
func NewCache(d time.Duration) *Cache {
	return &Cache{
		values:   make(map[string]*cacheItem),
		lifetime: d,
	}
}
// NewCache creates a new instance of Cache and defines the default lifetime for
// new cached items.