public static function get(string $key = null)
    {
        if (is_null($key)) {
            return static::$config;
        }
        // Key is formatted like database.default.driver
        $config = static::$config;
        $key = explode('.', $key);
        foreach ($key as $k) {
            if (!isset($config[$k])) {
                return null;
            }
            $config = $config[$k];
        }
        return $config;
    }