func createToken(completion: @escaping (String) -> () ){

    let currentUser = Auth.auth().currentUser
    currentUser?.getIDTokenForcingRefresh(true) { idToken, error in
      if let error = error {
        // Handle error

        completion("error")
        return;
      }

        var token = idToken ?? "empty"
        completion(token)
    }

}

// Using the func
var idToken = "empty"
let group = DispatchGroup()
 group.enter()

createToken() {token in
idToken = token
group.leave()
}
group.wait()
print(idToken)