Why async does not work on google Chrome mobile [phone]

Question

I am learning to work with async and I am testing the compatibility with old iphones, I am using the google Chrome of iphone 5s that is in version 92.0.4515 however I realized that async does not work, there is some correct way or is not available in old versions?

// Main.js
export async function hello(){
  alert("Hello " + navigator.userAgent)
}

// index.html
(async function(){
  const start = await import('./main.js');
  start.hello();
})();