WithExpiration of zero or negative value does not

The function comment says the following:

```go
// WithExpiration is an option to set expiration time for any items.
// If the expiration is zero or negative value, it treats as w/o expiration.
func WithExpiration(exp time.Duration) ItemOption {
```

However, setting 0 or -1 as the expiration causes the item to expire immediately, at odds with the documentation