lrucache

const metricsNamespace = "myservice"

// There are 2 types of entries will be stored in cache: users and posts.
const (
	cacheEntryTypeUser EntryType = iota
	cacheEntryTypePost
)

type User struct {
	ID   int
	Name string
}

type Post struct {
	ID    int
	Title string
}

// Make, configure and register Prometheus metrics collector.
metricsCollector := NewMetricsCollector(metricsNamespace)
metricsCollector.SetupEntryTypeLabels(map[EntryType]string{
	cacheEntryTypeUser: "user",
	cacheEntryTypePost: "post",
})
metricsCollector.MustRegister()

// Make LRU cache for storing maximum 1000 entries
cache, err := New[string](1000, metricsCollector)
if err != nil {
	log.Fatal(err)
}

// Add entries to cache.
cache.Add("user:1", User{1, "John"}, cacheEntryTypeUser)
cache.Add("post:1", Post{1, "My first post."}, cacheEntryTypePost)

// Get entries from cache.
if val, found := cache.Get("user:1", cacheEntryTypeUser); found {
	user := val.(User)
	fmt.Printf("%d, %s\n", user.ID, user.Name)
}
if val, found := cache.Get("post:1", cacheEntryTypePost); found {
	post := val.(Post)
	fmt.Printf("%d, %s\n", post.ID, post.Title)
}

Output:

1, John
1, My first post.