Node getting empty array as result when post request

I am testing my post method on Postman. Whenever I post the result it would display empty array []. I console logged it on the node side and it returns empty array as well.

CREATE TABLE users (
    user_id SERIAL PRIMARY KEY,
    username TEXT,
    email TEXT,
    password TEXT
)

INSERT INTO users (username, email, password) VALUES ($1, $2, $3);


app.post('/api/users', function(req, res, next) {
    db.post_user([req.body.username, req.body.email, req.body.password], function(err, user) {
        console.log(user);
        if(err) res.status(500).send(err);
        else res.json(user);
    })
})

I am not exactly sure why I am getting empty array instead of actual data passing in.

via Yh1234