How can to declare a type for get property by dot notation string(get('user.name'))

Question

interface User {name: string, age: Number, fav: {game: string, music: string}}

user: User = {name: 'foo', age: 18, fav: {game: 'action', music: 'classical'}}

function get<?>(key: ?): ? {
    return key.split('.').reduce((a, b) => a[b], user)
}

how to declare it?

type PickByDotNotation<TObject, TPath extends string> =
    TPath extends `${infer TKey extends keyof TObject & string}.${infer TRest}` ?
        PickByDotNotation<TObject[TKey], TRest> :
        TPath extends keyof TObject ?
            TObject[TPath] :
            never

I found it, but not work. i want to