标记为异步的函数始终返回Promise

Functions marked as async always return a Promise

来自 https://developer.mozilla. org/zh-CN/docs/Web/JavaScript/Reference/Statements/async_function

异步函数是通过事件循环异步操作的函数，该事件使用隐式Promise返回其结果.

An asynchronous function is a function which operates asynchronously via the event loop, using an implicit Promise to return its result.