Why is my MailKit/MimeKit code blowing up? Does MailKit support gmail and Oath2?

Question

Here is my code, which has a comment to show where an exception occurs. I have a working implementation using Google's APIs directly, but I would rather use MailKit is it is an much friendlier API and I'd like to support other providers, not just Google.

internal async Task GmailTestAsync()
{
    const string GMailAccount = "[email protected]";

    var clientSecrets = new ClientSecrets
    {
        ClientId = "yourclientid",
        ClientSecret = "yourclientsecret",
    };

    var codeFlow = new GoogleAuthorizationCodeFlow(new GoogleAuthorizationCodeFlow.Initializer
    {
        DataStore = new FileDataStore("CredentialCacheFolder", false),
        // Scopes = new[] { "https://mail.google.com/" }, maybe this works?
        Scopes = new[] { GmailService.Scope.GmailReadonly, GmailService.Scope.GmailSend },
        ClientSecrets = clientSecrets
    });

    var codeReceiver = new LocalServerCodeReceiver();
    var authCode = new AuthorizationCodeInstalledApp(codeFlow, codeReceiver);

    var credential = await authCode.AuthorizeAsync(GMailAccount, CancellationToken.None);

    if (credential.Token.IsExpired(SystemClock.Default))
        await credential.RefreshTokenAsync(CancellationToken.None);

    var oauth2 = new SaslMechanismOAuth2(credential.UserId, credential.Token.AccessToken);

    using (var client = new ImapClient())
    {
        await client.ConnectAsync("imap.gmail.com", 993, SecureSocketOptions.SslOnConnect);

        // next line throws exception
        await client.AuthenticateAsync(oauth2);
        /*
        MailKit.Security.AuthenticationException
            HResult=0x80131500
            Message=Authentication failed.
            Source=MailKit
            StackTrace:
            at MailKit.Net.Imap.ImapClient.<AuthenticateAsync>d__103.MoveNext()
            deleted...
        */
        await client.DisconnectAsync(true);
    }
}

Does MailKit support gmail and OAuth2? Is there some sample code somewhere? I have been following the code here: https://github.com/jstedfast/MailKit/blob/master/GMailOAuth2.md but I get a MailKit.Security.AuthenticationException at await client.AuthenticateAsync(oauth2);