与promise相关，await后面必须是一个promise，await拿到的是promise成功的结果，优点是可以像写同步代码一样去写异步代码，代码范例：
import axios from “axios”;
const onError = (reason) => {
handleError(reason)
throw reason
}
async function fetch() {
const response = await axios.get(‘/xxx’).catch(onError)
console.log(response)
}
