Koa2 with router and Hot Module Replacement

app.js

'use strict';

let Koa = require('koa');
let jsonBody = require('koa-json-body');
let router = require('./router');
let defaultErrorHandler = require('./default-error-handler');

module.exports = new Koa()
    .use(defaultErrorHandler)
    .use(jsonBody({ limit: '1mb', fallback: true, strict: true }))
    .use(router.routes())
    .use(router.allowedMethods())
    .on('error', function (err, ctx) {
        console.error(err, ctx);
    });

default-error-handler.js

'use strict';

module.exports = function (ctx, next) {
    return next().catch(function (err) {
        ctx.status = err.statusCode || err.status || 500;
        ctx.body = err.message;
    });
};

index.js

'use strict';

let http = require('http');

const PORT = process.env.PORT || 8080;
let currentApp = require('./app').callback();
let server = http.createServer(currentApp).listen(PORT, function () {
    console.log(`Server started on: http://localhost:${PORT}`);
});

if (module.hot) {
    module.hot.accept('./app', function () {
        try {
            server.removeListener('request', currentApp);
            currentApp = require('./app').callback();
            server.on('request', currentApp);
        } catch (err) {
            console.error(err);
        }
    });
    module.hot.accept();
    module.hot.dispose(function () {
        console.log('Server stopped');
        server.close();
    });
}

router.js

'use strict';

var Router = require('koa-router');
var router = new Router();

module.exports = router
    .get('/', function ({ request, response }) {
       response.body = '';
    });