I am trying to set the expiresIn function in my javascript app. I keep getting this error. Can anyone see what I am doing wrong?

  app.post('/login', async(req, res) => {
            const user = req.body.email;
            const accessToken = jwt.sign(user, process.env.ACCESS_TOKEN_PRIVATE, {
                expiresIn: '1d'
            });
            res.send({ accessToken });

        })

The issue seems to be simple but I don't know how to fix it, what am I doing wrong?