Use `fetch` with `async` and `await`

fetch.js

let getJson = async url => {
  try {
    let response = await fetch(url);
    let json = await response.json();
    return json;
  }
  catch(ex) {
    //throw ex; //may want to handle externally
    console.error(ex);
  }
};

//demo
let now = getJson('http://date.jsontest.com/');
console.log(now.time);  //should show current time