How to use wait-on

async function createServer (profilerEnabled, url) {
 const server = spawn(process.execPath, ['server'], {
  cwd: __dirname,
  env: {
   DD_PROFILING_ENABLED: String(profilerEnabled),
   PORT: url.port
  }
 })

 process.once('SIGINT', () => {
  server.kill('SIGINT')
 })

 await waitOn({
  timeout: 5000,
  resources: [url.href]
 })

 return server
}

function waitOnFile(filename) {
  return new Promise(function(resolve, reject) {
    waitOn(
      {
        resources: [filename],
        interval: 50,
        timeout: 500,
        window: 0
      },
      function(err) {
        if (err) {
          return reject(err);
        }
        return resolve();
      }
    );
  });
}