How to use the universal-analytics.middleware function in universal-analytics

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
app.enable('trust proxy')

if (process.env.MATOMO_URL) {
  console.log('Matomo Analytics activated');

  app.use(matomo({
    siteId: process.env.MATOMO_SITE,
    matomoUrl: process.env.MATOMO_URL,
    matomoToken: process.env.MATOMO_TOKEN
  }));
}

app.use(ua.middleware("UA-115902726-4", { cookieName: '_ga' }));
app.use(function (req, res, next) {
  if (!req.headers['x-forwarded-for']) {
      req.headers['x-forwarded-for'] = '0.0.0.0';
  }
  req.visitor.pageview({
    dp: req.originalUrl,
    dr: req.get('Referer'),
    ua: req.headers['user-agent'],
    uip: req.connection.remoteAddress
      || req.socket.remoteAddress
      || req.connection.remoteAddress
      || req.headers['x-forwarded-for'].split(',').pop()
  }).send()
  next();
});

app.use(favicon(path.join(__dirname, 'public/gi/img/favicon.ico'), { maxAge: oneDay }));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: true}));
app.use(methodOverride());

// development only
if ('development' == app.get('env')) {
  app.use(errorHandler());
}

// Route endpoints
routes(app);

// all environments
app.use(ua.middleware(process.env.GA_TRACKING_ID, {cookieName: '_ga'}));
app.use(express.static(path.join(__dirname, 'public'), { maxAge: oneDay }));
app.use(require('uglify-js-middleware')({ src: path.join(__dirname,'public') }));
app.use(require('less-middleware')(path.join(__dirname,'public'), [], [], [{compress: true}]));

// Start server
app.listen(app.get('port'), function() {
  console.log("Express server listening on port " + app.get('port'));
});

async function start() {

  const app = express();
  const cookieParser = require('cookie-parser');
  const bodyParser = require('body-parser');
  app.use(cookieParser());
  // Setup Google Analytics
  app.use(universalAnalytics.middleware(process.env.GA_ID, {cookieName: '_ga'}));
  app.use(bodyParser());
  app.use(logReqPerf);

  const server = http.Server(app);
  const io = require('socket.io')(server);
  app.set('socketio', io);

  // Init Nuxt.js
  const nuxt = new Nuxt(config)

  const {host, port} = nuxt.options.server

  // Build only in dev mode
  if (config.dev) {
    const builder = new Builder(nuxt)
    await builder.build()

const ga = (req, res, next) => {

  // We generate a session to be able to keep track of requests coming from the same visitor
  const session = expressSession({
    httpOnly: true,
    secret: 'b4;jP(cUqPaf8TuG@U',
    cookie: {
      secure: process.env.NODE_ENV === 'production' || process.env.NODE_ENV === 'staging',
      maxAge: 60*60*24*30*1000 // 1 month
    }
  });

  const mw = ua.middleware(config.GoogleAnalytics.account, {cookieName: '_ga'});

  session(req, res, () => {
    mw(req, res, next);
    req.ga = {
      pageview: () => req.visitor.pageview(req.url).send(),
      event: (EventCategory, EventName, EventLabel, EventValue) => req.visitor.event(EventCategory, EventName, EventLabel, EventValue, {p: req.url}).send()
    }
  });
};

visitor.item(449.99, 1, 'ID54321', 'T-Shirt', 'Blue', { ti: '123456' }).send();

visitor.pageview('/').send();
visitor.pageview('/').pageview('/contact').send();
visitor.pageview('/landing-page-1').event('Testing', 'Button color', 'Blue').send();
visitor.pageview('/landing-page-1').send();
visitor.event('Testing', 'Button color', 'Blue', 42, { p: '/landing-page-1' }).send();

visitor
    .event({ ec: 'Mail Server', ea: 'New Team Member Notification sent' })
    .event({ ea: 'Invitation sent' })
    .send();

visitor.set('uid', '123456789');

app.use(ua.middleware('UA-XXXX-Y', { cookieName: '_ga' }));

ua.createFromSession({ cid: 'some-string' });

ua('UA-XXXX-XX').debug();

ua('UA-XXXX-XX', {
    requestOptions: {
        proxy: '…',
    },
});