gulpfile.js

// Run PageSpeed Insights
gulp.task('pagespeed', function (cb) {
  // Update the below URL to the public URL of your site
  pagespeed.output('example.com', {
    strategy: 'mobile',
    // By default we use the PageSpeed Insights free (no API key) tier.
    // Use a Google Developer API key if you have one: http://goo.gl/RkN0vE
    // key: 'YOUR_API_KEY'
  }, cb);
});