[新手]在学习typescript时，在用到promise时候，遇到如下问题编译不通过，应该如何处理
An async function or method in ES5/ES3 requires the ‘Promise’ constructor. Make sure you have a declaration for the ‘Promise’ constructor or include ‘ES2015’ in your --lib option.
ts version 2.6 “target”: “es5”
