Six random numbers, but repeating? How not repeat? Swift

i have this code:

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

@IBAction func geraNumeros(_ sender: Any) {


    var numeroAleatorio:[Int] = []


    for _ in 1...6 {
        numeroAleatorio.append(Int(arc4random_uniform(60)+1))
    }

    numeroAleatorio.sort()



    labelNumeros.text = "\(numeroAleatorio[0]) - \(numeroAleatorio[1]) - \(numeroAleatorio[2]) - \(numeroAleatorio[3]) - \(numeroAleatorio[4]) - \(numeroAleatorio[5]) "

    }

@IBOutlet weak var labelNumeros: UILabel!

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

But sometimes numbers repeating, like:

10 - 18 - 12 - 10 - 30 - 60

Like 10-10, so what to do?