func NewObjectCache(f func() (interface{}, error), ttl time.Duration) *ObjectCache {
	return &ObjectCache{
		updater: f,
		cache:   expirationcache.NewTTLStore(stringKeyFunc, ttl),
	}
}

// stringKeyFunc is a string as cache key function
func stringKeyFunc(obj interface{}) (string, error) {
	key := obj.(objectEntry).key
	return key, nil
}

// Get gets cached objectEntry by using a unique string as the key.

	ttlPolicy := &expirationcache.TTLPolicy{TTL: ttl, Clock: clock}
	deleteChan := make(chan string, 1)
	return &ObjectCache{
		updater: f,
		cache:   expirationcache.NewFakeExpirationStore(stringKeyFunc, deleteChan, ttlPolicy, clock),
	}
}

func TestAddAndGet(t *testing.T) {
	testObj := testObject{
		key: "foo",
		val: "bar",
	}
	objectCache := NewFakeObjectCache(func() (interface{}, error) {