I am constantly getting error for this code cannot read property 'username' of undefined

Question

I am using node js package express js to store user input data and return username stored after user click submit button.

Server Error (http://localhost:3000/store-user): TypeError: Cannot read property 'username' of undefined

For app.js file :

const express = require('express');

const app = express();

//Change it to javascript object
app.use(express.urlencoded({extended: false}));

//Get request that send by browser
app.get('/currentime', function(req,res) {
    res.send('<h1>'+ new Date().toISOString() +'</h1>');

});  //localhost:3000/currenttime

app.get('/',function(req,res){
    res.send('<form action="/store-user" method="POST"><label>Your Name</label><input type="text" name="username"><button>Submit</button></form>');
})//localhost:3000/

app.post('/store-user', function(res,req) {
    const userName = req.body.username;
    console.log(userName);
    res.send('<h1>Username stored!</h1>');
});


app.listen(3000)