cors for koa extend.
$ npm install @koex/cors
// See more in test
import cors from '@koex/cors';
import * as Koa from 'koa';
const app = new Koa();
app.use(cors());
app.use(ctx => {
ctx.body = 'Hello, World!';
});
app.listen(8000, '0.0.0.0', () => {
console.log('koa server start at port: 8000');
});