Gulp: Useing ngrok with BrowserSync

gulpfile.js

// first run npm install ngrok - then put var ngrok = require('ngrok'); at the top of your gulpfile
var ngrok = require('ngrok');
var browserSync = require('browser-sync')
browserSync({
    server: "./app"
}, function (err, bs) {
   ngrok.connect(bs.options.get('port'), function (err, url) {
      // https://757c1652.ngrok.com -> 127.0.0.1:8080  
   }); 
});