1-1初始化 仓库1-2安装依赖1-3实现hello world 1-1初始化 仓库npm init -y 1-2安装依赖npm i koa -S 1-3实现hello worldconst koa = require('koa')const app = new koa()app.use(async ctx=>{ ctx.body="hello world"})app.listen(4000,()=>{ console.log('服务器打开了');})