动态import是异步的，同步和异步场景如何使用

// say.ts 
export function hi() { 
  console.log(`Hello`); 
} 
export function bye() { 
  console.log(`Bye`); 
}

import('./say').then(ns => {ns.hi(); ns.bye();});

async function test() { 
  let ns = await import('./say'); 
  let hi = ns.hi; 
  let bye = ns.bye; 
  hi(); 
  bye(); 
}