koarepl.js

const repl = require('repl')
const Koa = require('koa')
const app = new Koa()

app.context.defaultMsg = "Hello World"

app.use( ctx => ctx.body = app.context.defaultMsg )
app.listen(3000)

repl.start({prompt: '> ', eval: myEval});

function myEval(stdin, context, filename, stdout) {
    stdout(eval(stdin))
}