## 1.实现一个简单的路由 ~~~ const koa = require('koa') const Router = require('koa-router') //实例化koa const app = new koa() const router = new Router(); //路由 router.get('/',async ctx=>{ ctx.body = {msg:"hello world"} }).get('/user',async ctx=>{ ctx.body = "user" }) //启动路由 app.use(router.routes()).use(router.allowedMethods) const port = process.env.PORT || 5000; app.listen(port,()=>{ console.log(`server started on ${port}`); }) ~~~