Add button in navigation bar in swift

fucn viewDidLoad(_ animated:Bool){
        super.viewDisLoad(animated)
        let button = UIButton(type: .system)
        button.frame = CGRect(x: 0, y: 0, width: 30, height: 30)
        button.setTitle("check", for: UIControl.State.normal)
        navigationItem.leftBarButtonItem = UIBarButtonItem(customView: button)
        //navigationItem.rightBarButtonItem = UIBarButtonItem(customView: button)

}