Need help with app.get('/') not being called

I am working on implementing cookies to allow multiple users to be logged in simultaneously. Currently, users can log in successfully. However, upon refreshing the page, all users get logged in as the same user (the last one who logged in). I suspect that this issue is related to app.get('/') not being triggered.

Below is the code I have. It's a bit lengthy, and I'm not sure which parts may impact the functionality of the app.get function.

let mysql = require("mysql2");

// Including express in our project
const express = require("express");
const sessions = require("express-session");
const cookieParser = require("cookie-parser");
const bodyParser = require("body-parser");
const { SourceMap } = require("module");
const { errorMonitor } = require("events");
const { receiveMessageOnPort } = require("worker_threads");
const bcrypt = require("bcrypt");
const { match } = require("assert");
const path = require("path")

// Creating an instance of our application by calling the express function
const app = express();

// Adding HTTP and calling its server function while passing our express app
const http = require("http").Server(app);
// Adding IO, passing socket.io reference and referencing http
const io = require("socket.io")(http);

app.use(express.json());
app.use(express.urlencoded({extended: true}));

app.use(cookieParser());

const oneDay = 1000 * 60 * 60 * 24;

app.use(sessions({
    secret: "secret key",
    saveUninitialized: true,
    cookie: { maxage: oneDay },
    resave: false,
}))

// Concentrating data for easy reading. If you're curious 
// about what extended does, visit body-parser on npmjs.com
// and scroll down to the extended section.
app.use(bodyParser.urlencoded({extended: false}));

app.use(express.json());
app.use(express.urlencoded({ extended: true }));

let connection = mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "MyPassword",
    database: "slutprojekt",
});

var session;

const dirname = './webbsidan'

console.log(__dirname)

// Setting the destination when someone 
// visits our web server. In this case,
// the person will land in a folder named
// 'webbsidan' where I'll place html documents,
// css, images, etc.
app.use(express.static(path.join(__dirname, '/webbsidan')))

app.get('/', (req, res) => {
    console.log('get /')
    // console.log(req)
    session = req.session;
    
    var Referer = "";
    
    if (req.rawHeaders.indexOf('Referer') != -1){
        
        Referer = req.rawHeaders[req.rawHeaders.indexOf('Referer')+1].split('/')
        Referer = Referer[Referer.length-1]
    }

    console.log(Referer)

    if (Referer != 'login.html' && !session.user){
        res.sendFile('/webbsidan/login.html', {root: __dirname})
    } else if (Referer == 'login.html' && session.user){
        res.sendFile('/webbsidan/index.html', {root: __dirname})
    }
})

app.post('/login', (req, res) => {
    console.log('login-post received');    

    let sql ="SELECT * FROM användare"

    connection.query(sql, function (err, result, fields) {
        if (err) throw err;
        let loggedIn = false

        for (const object of result){
            if (object.AnvändarNamn == req.body.username){
                
                if (bcrypt.compareSync(req.body.password, object.Lösenord)){
                    
                    loggedIn = true;
                    
                    session=req.session;
                    session.user=req.body.username;
                    session.userid=object.AnvändarID;
                    session.sid=req.rawHeaders[req.rawHeaders.indexOf('Cookie')+1]
                    // console.log(req.session)
                    
                    res.redirect('/');
                }
                else {
                    // console.log("incorrect password")
                }
                break;
            }
            else {
                // console.log('username incorrect:', object.AnvändarNamn);
            }
        }
        if (loggedIn == false){
            res.send('<script>alert("Login failed, try again"); window.location.replace("login.html")</script>')
        }
    })
})
...

// Instead of app.listen, we now run http.listen
http.listen(3000, () => {
    console.log("Server is running, visit http://localhost:3000");
});

function genDates(start, end){
    var getDaysArray = function(start, end) {
        for(var arr=[],dt=new Date(start); dt<=new Date(end); dt.setDate(dt.getDate()+1)){
            arr.push(new Date(dt));
        }
        return arr;
    };

    var newStart = start.toISOString().replace("00:00:00", "10:10:10") // specify time so that no date is skipped or repeated when 
    var newEnd = end.toISOString().replace("00:00:00", "10:10:10") // time is shifted in march and october
    
    var daylist = getDaysArray(newStart, newEnd);

    var datelist= []

    daylist.forEach(element => {
        datelist.push(element.toISOString().split("T")[0])
    })

    var dowNameList = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'];

    let sql1 = `SELECT dateID, fullDate FROM kalender`
    connection.query(sql1, function (err, result, fields) {
        if (err) throw err;
        
        for (let i = 0; i < daylist.length; i++){
            
            var dowName = daylist[i].toString().split(" ")[0]
            var dowNum = dowNameList.indexOf(dowName)
            
            dowNum += 1
            
            const found = result.some(el => el.fullDate == datelist[i]) // Check if date already exists in database
            
            if (!found){
                let sql2 = `INSERT INTO kalender (dateID, fullDate, dowName, dowNum) VALUES (${i+1}, '${datelist[i]}', '${dowName}', ${dowNum});`
                connection.query(sql2, function (err, result, fields) {
                    if (err) throw err;
                })
            }
        }
    })
}

genDates(new Date("2023-01-01"),new Date("2023-12-31"));