Saved from https://stackoverflow.com/questions/44461082/how-to-configure-rewrite-rules-inside-firebase-hosting-to-route-certain-requests

firebase2

var functions = require('firebase-functions');
var express = require('express');

var app = express();
var router = express.Router();

router.post('/register', registerFunction);
router.post('/verify', verifyFunction);

app.use('/fns', router);

exports.fns = functions.https.onRequest(app);