laravel中，session存在跨域問題，可使用中介軟體解決

在app/Http/Kernel.php的中介軟體中加入以下程式碼

protected $middleware = [
    \Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::class,
    \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
    \App\Http\Middleware\TrimStrings::class,
    \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
    \App\Http\Middleware\TrustProxies::class,

    \Illuminate\Cookie\Middleware\EncryptCookies::class,
    \Illuminate\Session\Middleware\StartSession::class,
];

重要的2條：
\Illuminate\Cookie\Middleware\EncryptCookies::class,
\Illuminate\Session\Middleware\StartSession::class,