for i := 0; i < numBuckets; i++ {
		res.buckets[i] = bucket[K, V]{entries: make(map[K]*Entry[K, V])}
	}

	// enable deleteExpired() running in separate goroutine for cache with non-zero TTL
	//
	// Important: done channel is never closed, so deleteExpired() goroutine will never exit,
	// it's decided to add functionality to close it in the version later than v2.
	if res.ttl != noEvictionTTL {