laraval关于session失效问题
Kernel.php中开启Session
```
protected $middleware = [
\App\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\Session\Middleware\StartSession::class,
}
```
切忌是先运行构造方法在走session 这种顺序！！！
