co is awesome!!!!!

firstco.js

    insertOrderItem(req, reply) {
        const order_id = req.payload.order_id;
        const product_id = req.payload.product_id;
        const msg = new message();
        co(function*() {
            const product = yield Product.get({ _id: product_id });
            const menu = yield Menu.get({ _id: product.menu_id });
            const order_item_doc = yield new Orderitem({
                is_add: true,
                order_id: order_id,
                menu_id: menu._id,
                menu_name: menu.name,
                product_id: product._id,
                product_name: product.name,
                price: product.price,
                img: product.img_url,
                spec: product.unit,
                total: product.price,
                actual_payment: product.price,
                printer_num: menu.printer_num
            });
            const order_item = yield order_item_doc.save();
            const total = yield this.updateOrderTotal(order_id);
            return reply(msg.success(total));
        }).catch(err => {
            console.error(err);
            return reply(msg.fail(err))
        });
    },