Export NewItem function

[hasfjord]

There might be multiple reasons for creating an Item object manually. Now the only way of creating such an object is to add it to the cache, which might not always be ideal.
My use-case is allowing a workaround for loader error handling.

By storing the error in the value it could be inspected by the caller of the get function.

Cached function:

type cachedValue struct {
	usefulString string
	Err          error
}

Loader:

loader := ttlcache.LoaderFunc[string, *cachedValue](
		func(c *ttlcache.Cache[string, *cachedValue], key string) *ttlcache.Item[string, *cachedValue] {
			v, err := SomethingThatCouldFail()
			if err != nil {
				return ttlcache.NewItem(key, cachedValue{"", err}, 0, false)
			}
			return c.Set(key, v, 1*time.Hour)
		})

Cache setup:

cache := ttlcache.New(
		ttlcache.WithTTL[string, *cachedValue](1*time.Hour),
		ttlcache.WithLoader(loader),
	)

Get call:

// Get the value from the cache
item := cache.Get("key").Value()
if item.Err != nil {
	//handle error
}
// use item.Value().usefulString

I would prefer the loader function returning an error in addition to the error, but that would break the current api contract.

[swithek]

I quite like the loader error workaround in your example. There's just one small change that we need to make:

[swithek]

Regarding the loader interface and errors: we have this issue, feel free to upvote it/share your ideas there as well.

[swithek]

Thank you for your contribution @hasfjord.