1. koa2 脚手架   https://www.jianshu.com/p/4479dda7912a

2. npm install routing-controllers   npm install reflect-metadata  npm install koa @koa/router koa-bodyparser @koa/multer  npm install -D @types/koa @types/koa-bodyparser

3. npm i --save-dev @types/node   npm install --save-dev cross-env