1.连接mongoDB
https://blog.csdn.net/oak160/article/details/79571906
2.设置redis与session
https://www.cnblogs.com/samsimi/p/6547452.html
涉及到的指令
//mongodb内容
npm install --save koa //koa安装
npm install --save koa-bodyparser //koa的参数解析中间件
npm install --save koa2-cors //koa的跨域中间件
npm install --save koa-router //koa的路由映射
npm install --save mongodb //mongodb
npm install --save mongoose //mongoose
//redis与session内容
npm install --save koa2-cookie-session //koa2-cookie-session,替代express-session
npm install --save koa-session-redis //koa-session-redis session存到redis
npm install --save ioredis //连接redis
