const mount = require('koa-mount');
const Koa = require('koa');
const a = new Koa();
a.context.test = "hallo";
a.use(async function (ctx, next){
ctx.body = "test:" + ctx.test;
return next();
});
// app
const app = new Koa();
app.use(mount('/hello', a));
app.listen(3000)
a.listen(3001);