购物车创建外键约束出现了问题

首页抱歉，今晚有点不太适合写代码，遇到这个问题，我也很无赖

 public function up()
    {
        Schema::create('cart_items', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->unsignedBigInteger('user_id');
            $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
            $table->unsignedBigInteger('product_sku_id');
            $table->foreign('product_sku_id')->references('id')->on('product_skus')->onDelete('cascade');
            $table->unsignedInteger('amount');
        });
    }

请@leo 看看我这个应该从哪里去找问题