How to create a background service for location tracking in kotlin

Question

I have the following code for fetching latitude and longitude in kotlin:

    class MainActivity : AppCompatActivity(), GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, com.google.android.gms.location.LocationListener {

    private val TAG = "MainActivity"
    private lateinit var mGoogleApiClient: GoogleApiClient
    private var mLocationManager: LocationManager? = null
    lateinit var mLocation: Location
    private var mLocationRequest: LocationRequest? = null
    private val listener: com.google.android.gms.location.LocationListener? = null
    private val UPDATE_INTERVAL = (2 * 1000).toLong()  /* 10 secs */
    private val FASTEST_INTERVAL: Long = 2000 /* 2 sec */

    lateinit var locationManager: LocationManager



    override fun onStart() {
        super.onStart();
        if (mGoogleApiClient != null) {
            mGoogleApiClient.connect();
        }
    }

    override fun onStop() {
        super.onStop();
        if (mGoogleApiClient.isConnected()) {
            mGoogleApiClient.disconnect();
        }
    }

    override fun onConnectionSuspended(p0: Int) {

        Log.i(TAG, "Connection Suspended");
        mGoogleApiClient.connect();
    }

    override fun onConnectionFailed(connectionResult: ConnectionResult) {
        Log.i(TAG, "Connection failed. Error: " + connectionResult.getErrorCode());
    }

    override fun onLocationChanged(location: Location) {


        var msg = "Updated Location: Latitude " + location.longitude.toString() + location.longitude;
        txt_latitude.setText(""+location.latitude);
        txt_longitude.setText(""+location.longitude);
        Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();


    }

    override fun onConnected(p0: Bundle?) {

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            return;
        }


        startLocationUpdates();

        var fusedLocationProviderClient : 
                 FusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this);
        fusedLocationProviderClient .getLastLocation()
                .addOnSuccessListener(this, OnSuccessListener<Location> { location ->
                    // Got last known location. In some rare situations this can be null.
                    if (location != null) {
                        // Logic to handle location object
                        mLocation = location;
                        txt_latitude.setText("" + mLocation.latitude)
                        txt_longitude.setText("" + mLocation.longitude)
                    }
                })
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        MultiDex.install(this)

        mGoogleApiClient = GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build()

        mLocationManager = this.getSystemService(Context.LOCATION_SERVICE) as LocationManager

        checkLocation()
    }

    private fun checkLocation(): Boolean {
        if(!isLocationEnabled())
            showAlert();
        return isLocationEnabled();
    }

    private fun isLocationEnabled(): Boolean {
        locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager
        return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) || locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)
    }

    private fun showAlert() {
        val dialog = AlertDialog.Builder(this)
        dialog.setTitle("Enable Location")
                .setMessage("Your Locations Settings is set to 'Off'.\nPlease Enable Location to " + "use this app")
                .setPositiveButton("Location Settings", DialogInterface.OnClickListener { paramDialogInterface, paramInt ->
                    val myIntent = Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS)
                    startActivity(myIntent)
                })
                .setNegativeButton("Cancel", DialogInterface.OnClickListener { paramDialogInterface, paramInt -> })
        dialog.show()
    }

    protected fun startLocationUpdates() {

        // Create the location request
        mLocationRequest = LocationRequest.create()
                .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
                .setInterval(UPDATE_INTERVAL)
                .setFastestInterval(FASTEST_INTERVAL);
        // Request location updates
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient,
                mLocationRequest, this);  
    }
}

I cannot create this as a background service. I need a background service for fetching location. I am working on a project in which I need to fetch location in background even when the user locks his/her phone or closes the app.