Swift. How to choose a random user from Firebase Database?

I have a Firebase Database, every users data is being stored, now in my app I want to be able to choose a random user from the database how can I do that?

This is my JSON tree from my database:

{
  "users" : {
    "bge8yeAx8FedX8ozXRGl5ltWkbD3" : {
      "Coins" : 0,
      "Dollars" : 0,
      "GamesLost" : 0,
      "GamesWon" : 0
    },
    "lzsPuNwHbIZI1J8k40FspYRV4XQ2" : {
      "Coins" : 52,
      "Dollars" : 46,
      "GamesLost" : 0,
      "GamesWon" : 0
    }
  }
}