使用koa的时候报错

[muzishuiji]

koa deprecated Support for generators will be removed in v3. See the documentation for examples of how to convert old middle
ware https://github.com/koajs/koa/blob/master/docs/migration.md index.js:5:5

错误信息是上面这样的，我打开那个链接想按照说明升级middleware，但是没看懂怎么弄，望大神指教