npm init -y npm i -S koa@2 创建app.js文件，代码如下：const Koa = require('koa') const app = new Koa() app.use(async (ctx,next) => { const start = new Date() console.log('[logger middleware] before await ...') await next() console.log('[logger middleware] after await ...') con- 阅读剩余部分 -