Creating 4 digit number with no repeating elements in Kotlin

I'm aware this question exists here:

Creating a 4 digit Random Number using java with no repetition in digits

but I'm new to Kotlin and would like to explore the direct Kotlin features. So as the title suggests, I'm trying to find a Kotlin specific way to nicely solve generate a 4 digit number (after that it's easy to make it adaptable for length x) without repeating digits.

This is my current working solution and would like to make it more Kotlin. Would be very grateful for some input.

fun createFourDigitNumber(): Int {
  var fourDigitNumber  = ""
  val rangeList = {(0..9).random()}

  while(fourDigitNumber.length < 4)
  {
   val num = rangeList().toString()
    if (!fourDigitNumber.contains(num)) fourDigitNumber +=num
  }

  return fourDigitNumber.toInt()
}