Swift MailCore2 GTMAppAuth Allowing Less Secure App Access - swift

Question

I am building a test app using MailCore2 and GTMAppAuth, and I bumped into this error:
A stable connection to the server could not be established.
I followed various SO posts, like this, this and this, and so I think my code should be correct. My implementation are as follows:
//At AppDelegate
var currentAuthorizationFlow: OIDAuthorizationFlowSession?
func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool
{
if currentAuthorizationFlow!.resumeAuthorizationFlow(with: url) {
self.currentAuthorizationFlow = nil
return true
}
return false
}
class ViewController: UIViewController {
let kIssuer = "https://accounts.google.com"
let kClientID = "\(MY_CLIENTID).apps.googleusercontent.com"
let kRedirectURI = "com.googleusercontent.apps\(MY_CLIENTID):/oauthredirect"
let kExampleAuthorizerKey = "googleOAuthCodingKey"
override func viewDidLoad() {
super.viewDidLoad()
authenticateGmail()
}
func authenticateGmail() {
let issuer = URL(string: kIssuer)!
let redirectURI = URL(string: kRedirectURI)!
let appDelegate = UIApplication.shared.delegate as! AppDelegate
OIDAuthorizationService.discoverConfiguration(forIssuer: issuer) { (configuration, error) in
//handleError
if let configuration = configuration {
let scopes = [OIDScopeOpenID, OIDScopeProfile, "https://mail.google.com/"]
let request = OIDAuthorizationRequest(configuration: configuration, clientId: self.kClientID, scopes: scopes, redirectURL: redirectURI, responseType: OIDResponseTypeCode, additionalParameters: nil)
appDelegate.currentAuthorizationFlow = OIDAuthState.authState(byPresenting: request, presenting: self, callback: { (authState, error) in
//handleError
if let authState = authState {
if let accessToken = authState.lastTokenResponse?.accessToken {
NSLog("Successfully authenticated: %#", accessToken)
self.fetchEmailsFromGmail(accessToken: accessToken)
}
}
})
}
}
}
func fetchEmailsFromGmail(accessToken: String) {
let session = MCOIMAPSession()
session.hostname = "imap.gmail.com"
session.port = 993
session.username = "XXX#\(COMPANY_DOMAIN)"
session.authType = .xoAuth2
session.connectionType = .TLS
session.oAuth2Token = accessToken
let fetchFolderOperation = session.fetchAllFoldersOperation()
fetchFolderOperation?.start({ (error, folders) in
//handleError
if let folders = folders, !folders.isEmpty {
print(folders)
}
})
}
My implementation allows me to authenticate successfully, ie there is an accessToken printed. But when it attempts to fetch folders, it throws:
A stable connection to the server could not be established.
The thing is, it is possible to solve this by doing both the following:
allowing less secure app access via the Googles Accounts page
follow this solution here
However, these methods are not really safe methods in my opinion. I do not recall needing to do any of these when I connect up my email to other email clients, ie Outlook etc, so I do not view the above as real solutions.
Could anyone advice? Is there something wrong with my code, or I really have to resort to doing both steps above?