Add cache hit field in Item

[zacscoding]

Add cache hit field in Item.

Hello :) I want to record cache metrics with labels when calling Once function like below

    item := &Item{}
    if err := cache.Once(item); err != nil {
        return err
    }

    metrics.IncCacheTotal("product")
    if item.CacheHit {
        metrics.IncCacheHit("product")
    }

I found Stats() function but this function provides only total count of hits and misses :(