blacklist.go
func NewLRUBlacklist(cap int) (Blacklist, error) {
	c, err := lru.New(cap)
	if err != nil {
		return nil, err
	}

	b := &LRUBlacklist{lru: c}
	return b, nil
}
func NewLRUBlacklist(cap int) (Blacklist, error) {
	c, err := lru.New(cap)
	if err != nil {
		return nil, err
	}

	b := &LRUBlacklist{lru: c}
	return b, nil
}
// NewLRUBlacklist creates a new LRUBlacklist with capacity cap