How do I wait for a promise to resolve?

test.js

browser.webNavigation.onBeforeNavigate.addListener(e => {
  let originalUrl = e.url;
  console.log("Original URL: " + originalUrl);
  let replaceRe = /(.*)coolSite/(.*)/;
  let newUrl = originalUrl.replace(replaceRe, "$1coolerSite$2");
  
  async function checkUrl(){
    try {
      let response = await fetch(newUrl, {method: "HEAD"});
      if(!response.ok){
        console.log("Received status: " + response.status + " from cooler site");
        newUrl = originalUrl;
      }
    }
    catch(err) {
      console.log("Received error: " + error.toString() + " from cooler site");
      newUrl = originalUrl;
    }
  }
  
  checkUrl();
  
  browser.tabs.update(e.tabId, {url: newUrl});
});

async function check(url) {
    try {
        const r = await window.fetch(url);
        if (!r.ok) {
            console.log("Response not OK")
        }

        console.log("Response OK")
    } catch (err) {
        console.log("Error" + err.toString())
    }
}

async function foo(url) {
    await check(url);
    console.log("Finished checking")
}

foo("https://gist.github.com/quanticle/ae616593115b91ec9a114ece90d4bbdb")