[解決済み] await は非同期関数でのみ有効です。

// My function
const myfunction = async function(x, y) {
  return [
    x,
    y,
  ];
}

// Start function
const start = async function(a, b) {
  const result = await myfunction('test', 'test');
  
  console.log(result);
}

// Call start
start();

async function myfunction() {
  console.log('Inside of myfunction');
}

// Here we wait for the myfunction to finish
// and then returns a promise that'll be waited for aswell
// It's useless to wait the myfunction to finish before to return
// we can simply returns a promise that will be resolved later

// useless async here
async function start() {
  // useless await here
  return await myfunction();
}

// Call start
(async() => {
  console.log('before start');

  await start();
  
  console.log('after start');
})();

async function myfunction() {
  console.log('Inside of myfunction');
}

// Here we wait for the myfunction to finish
// and then returns a promise that'll be waited for aswell
// It's useless to wait the myfunction to finish before to return
// we can simply returns a promise that will be resolved later

// Also point that we don't use async keyword on the function because
// we can simply returns the promise returned by myfunction
function start() {
  return myfunction();
}

// Call start
(async() => {
  console.log('before start');

  await start();
  
  console.log('after start');
})();