main.ts

type modA = typeof import('./module-a');

function call(mod: modA) {
  const src = 'hello';
  const result = mod.id(src);
  console.log(`${src} -> ${result}`);
}

async function start() {
  console.log('start');
  const mod: modA = await import('./module-a');
  call(mod);
}

start();

module-a.ts

console.log('module a');

export function id(value: string): string {
  return value
}

export default {id}