public function createService(ServiceLocatorInterface $serviceLocator)
    {
        $config     = $serviceLocator->get('BjyAuthorize\Config');
        $cacheKey   = empty($config['cache_key']) ? 'bjyauthorize_acl' : (string) $config['cache_key'];

        return function () use ($cacheKey) {
            return $cacheKey;
        };
    }