最近在学习使用koa2,在尝试用koa2复写之前用express写的一个入口文件的时候发现命令行报错ctx.render is not a function

项目路径如下
//使用koa复写入口文件
const Koa = require('koa');
const Router = require('koa-router');
const koaBody = require('koa-body');
const views = require('koa-views');
const serve = require('koa-static');
const app = new Koa();
const router = new Router();
app.use(serve(__dirname));
app.use(koaBody()).use(router.routes());
app.use(views(__dirname + '/views/pages',{
extension: 'pug'
}))
app.listen(3000);
router.get('/', async(ctx, next) => {
await ctx.render("index",{
title:"nodeWeb 首页"
})
});