How to hold return until DEVICE_DISCOVERY_FINISHED in adnroid

Hi i am quite new to android development and using some native code in flutter. So i have called this function to scan bluetooth devices in MainActivity.kt.

    private fun scanBluetooth(): Set<String> {
        var foundDevices = mutableSetOf<String>()
        var isFinished = false

        val bluetoothAdapter: BluetoothAdapter? = BluetoothAdapter.getDefaultAdapter()

        bluetoothAdapter?.startDiscovery()

        var filter = IntentFilter(BluetoothDevice.ACTION_FOUND)
        filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED)

        val receiver = object : BroadcastReceiver() {
            override fun onReceive(context: Context, intent: Intent) {
                val action: String = intent.action
                when(action) {
                    BluetoothDevice.ACTION_FOUND -> {
                        val device: BluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE)
                        val deviceName = device.name
                        val deviceHardwareAddress = device.address // MAC address
                        val rssi = intent.getShortExtra(BluetoothDevice.EXTRA_RSSI, Short.MIN_VALUE)
                        foundDevices.add("${deviceHardwareAddress} ${rssi}")
                    }
                    BluetoothAdapter.ACTION_DISCOVERY_FINISHED -> {
                        isFinished = true;
                    }
                }
            }
        }
        registerReceiver(receiver, filter)
        
        return foundDevices
    }

So i want to return foundDevices only when BluetoothAdapter.ACTION_DISCOVERY_FINISHED is finished. Can you suggest a way how to achieve this?

android
I have tried something like this but getting errors.

    return when (isFinished) {
        true -> {
            unregisterReceiver(receiver)
            return foundDevices
        }
    }