async function apiController(req, res){
      const response = await request.get('http://...........)
      res.status(200).json({...})

app.get('/myurl', function (req, res) {
    makeApiRequest().then(result => {
        // We reach here after we are all done with the API.
        res.send('here is a response to browser using data from result');
    });
});

async function makeApiRequest() {
    // here, make the API request, do a polling loop, etc.
    // eventually return the result
}

- Browser client makes JSON request to your server.
- Server makes API call to service, gets back a 'request id'.
- Server sends back request id to browser client.
- Browser client enters loop, every 5 seconds, it sends server a message.
  - 'Did my request id complete yet?'
  - Server takes request id, asks service 'what is the answer?'
  - Send response back to browser.
- Browser client loops until the request is complete, then continues.