req.session keeps returning undefined - node.js

Question

I am new to cookies and session in express and I have a problem I don't understand how to solve. I make a simple user login system which communicate with DB. My login call works fine, but when I try to recuperate the value in req.session.user, it always return undefined when I call it in /getevents or /addevent.
const express = require("express");
const mysql = require("mysql");
const cors = require("cors");
const cookieParser = require("cookie-parser");
const session = require("express-session");
const bcrypt = require("bcrypt");
const saltRounds = 10;
const app = express();
app.use(express.json());
app.use(
cors({
origin: ["http://localhost:3000"],
methods: ["GET", "POST"],
credentials: true,
})
);
app.use(cookieParser());
app.use(
session({
key:"userId",
secret: "123123123",
resave: true,
saveUninitialized: true
}));
const db = mysql.createConnection({
database: 'defaultdb',
host: "dbhost.com",
port: 12345,
user: "db_user",
password: "password"
});
app.post("/login", (req, res) => {
const username = req.body.username;
const password = req.body.password;
db.query(
"SELECT * FROM user WHERE username = ?;",
[username],
(err, result) => {
if (err) {
res.send({ err: err });
}
if (result.length > 0) {
bcrypt.compare(password, result[0].password, (error, response) => {
if (response) {
req.session.userId = result[0].id;
res.send(result);
} else {
res.send({ message: "Invalid username / password !" });
}
});
} else {
res.send({ message: "Username does not exist !" });
}
}
);
});
app.get("/getevents", (req, res) => {
db.query(
"SELECT title, date FROM events WHERE user_id =?;",
req.session.userId,
(err, result) => {
if (err) {
console.log(err);
}
else {
res.send(result);
}
}
);
});
app.post("/addevent", (req, res) => {
db.query(
"INSERT INTO event (title,date,user_id) VALUES (" + req.body.title + ", " + req.body.date + ", " + parseInt(req.session.userId) + ")",
(err, result) => {
if (err) {
console.log(err);
}
else {
res.send(result);
}
}
);
})
After trying to resolve for a few hours I'm kind of out of ideas...