How can I host my CSS and index.html file into my local server by using node

Question

I just created a very simple landing page. I intended to practice my node skills and try to host the static website into my local server by using node. This is my file structure:

On my mac desktop. Inside NodeWebTest:

./assests
./css
./sass
index.html

But when I try to run it with my node code, my local server just running and cannot stop. What happen? How can I fix it?

var express = require('express');
var app = express();
var path = require('path');

app.use(express.static(__dirname + '/css'));
app.use(express.static(__dirname + '/assets'));

app.get('/', function(req, res) {

    // res.sendFile(path.join(__dirname + '/index.html'));

    res.writeHead(200, {"Content-Type": "./index.html"});


});


app.listen(3000);