public static function get(string $key = null)
    {
        self::set();

        if (empty($key)) {
            return self::$config;
        }

        $keys  = explode('.', $key);
        $value = self::$config;

        foreach ($keys as $key) {
            if ( ! isset($value[$key])) {
                return null;
            }

            $value = $value[$key];
        }

        return $value;
    }