branco para arquivo carregado

async function getFile() {
  let myPromise = new Promise(function(resolve) {
    let req = new XMLHttpRequest();
    req.open('GET', "mycar.html");
    req.onload = function() {
      if (req.status == 200) {
        resolve(req.response);
      } else {
        resolve("File not Found");
      }
    };
    req.send();
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

getFile();
Xanthous Xenomorph