Google Drive - View Controller - Add Scope

DriveViewController_Scopes.swift

import GoogleSignIn
import GoogleAPIClientForREST
import GTMSessionFetcher

class ViewController: UIViewController {
    let googleDriveService = GTLRDriveService()

    override func viewDidLoad() {
        // ...
        GIDSignIn.sharedInstance()?.scopes = [kGTLRAuthScopeDriveFile]
        // ...
    }
}