Return value from HTTP Post response in NodeJS

Question

I am trying to write a function that will just return part of the JSON response to the calling function. This is what I have

function returnToken()
{
    var https = require('follow-redirects').https;
var fs = require('fs');

var qs = require('querystring');

var options = {
  'method': 'POST',
  'hostname': hostname,
  'path': path,
  'headers': {
    'Accept': 'application/json',
    'Content-Type': 'application/x-www-form-urlencoded',
    'Cookie': 'AWSALBTG=VQeZ4MBoHfHiCgR7g4DBcvuSGVQgDKDPo95l9tiNlSv9WNmDW1Z6PqXjKOTP3LKeqkHw5//8vIH304VbApkBRePHFM8JVgOtmqpRpv9iVN+cYS73RiNl+kxWSnntRZQ4+oXnFkG5NVlZty+ohK8qyX1UhQDT5+UGhV9Kn9heLkbG; AWSALBTGCORS=VQeZ4MBoHfHiCgR7g4DBcvuSGVQgDKDPo95l9tiNlSv9WNmDW1Z6PqXjKOTP3LKeqkHw5//8vIH304VbApkBRePHFM8JVgOtmqpRpv9iVN+cYS73RiNl+kxWSnntRZQ4+oXnFkG5NVlZty+ohK8qyX1UhQDT5+UGhV9Kn9heLkbG'
  },
  'maxRedirects': 20
};

var req = https.request(options, function (res) {
  var chunks = [];

  res.on("data", function (chunk) {
    chunks.push(chunk);
  });

  res.on("end", function (chunk) {
    var body = Buffer.concat(chunks);
    console.log(JSON.parse(body).access_token);
    return JSON.parse(body).access_token;
  });

  res.on("error", function (error) {
    console.error(error);
  });
});

var postData = qs.stringify({
  'client_id': clientID,
  'client_secret': clientSecret,
  'scopes': scope,
  'grant_type': 'client_credentials'
});

req.write(postData);

req.end();

}

const t=returnToken();
console.log('t='+t);

When I run this code, the function runs and then outputs the access_token to the console just fine. However, by putting return JSON.parse(body).access_token; in the code where I did, I thought it would return the access function to the calling code. It doesn't. t is undefined. I'm kind of at a loss as to how to return that value.