A sample program that demonstrates how async await works in javascript.

async-await-hello-world.js

//Rentrant function. - Software terminology
//generator functions. - javascript terminology ()
//Read more here https://codeburst.io/understanding-generators-in-es6-javascript-with-examples-6728834016d5

function wait() {
    return new Promise(resolve => setTimeout(resolve, 3000));
}

async function sayAwaitHello() {
    await wait();
    console.log("Hello World");
}

async function main() {
    console.log("Before function call");
    await sayAwaitHello();
    console.log("After function call");
}

console.log("Before main");
await main();
console.log("After main");

 /**
  * Actual output
  * --------------
  * Before main
  * Before function call
  * After main
  * Hello World
  * After function call
  */

/**
 * Expected output
 * ------------------
 * Before main
 * Before function call
 * ...3 sec delay...
 * Hello world
 * After function call
 * After main
 */