How to make callback/coroutines in Method Channel in Kotlin?

Question

I'm trying to make callback to return data by method channel (because I will get the data after another function will activate), but returning variable is already callback. What should I do?

Kotlin MethodChannel code:

val list: MutableList<String> = ArrayList1()

 override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
         GeneratedPluginRegistrant.registerWith(flutterEngine);
         super.configureFlutterEngine(flutterEngine)

         MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL)
             .setMethodCallHandler { call: MethodCall, result: Result? ->
                 pendingResult = result
                 if (call.method == "createChannel") {
                  
                     //**my code**
 
                 } else if (call.method == "loginChannel") {
                     if (userLogged == false) {

                         //**this is what I want to put in callback**
                         result?.success(list.toString())
 
                         Toast.makeText(this, list.toString(), Toast.LENGTH_LONG).show()
                     }
                 }
             }
     }