public function get($key, $default = null)
    {
        \WildWolf\Cache\Validator::validateKey($key);

        if (isset($this->cache[$key])) {
            list($data, $expires) = $this->cache[$key];

            if (null === $expires || (new \DateTime()) < $expires) {
                return $data;
            }

            unset($this->cache[$key]);
        }

        return $default;
    }