ts Cannot find name 'async' via TypeScript

I'm using TypeScript But I have This Error:

[ts] Cannot find name 'async'

And This is my Code:

async someAsyncCode() {
    let asyncFn = () => {
        return new Promise((resolve: Function) => { resolve(2); });
    }
    // should log `2`
    console.log(await asyncFn());
}

via Sedric Heidarizarei