public static IAppBuilder UseGitHubAuthentication(
     this IAppBuilder app,
     GitHubAuthenticationOptions options)
 {
     return UseAuthentication(
         typeof(OAuth2AuthenticationMiddleware<GitHubAuthenticationHandler, GitHubAuthenticationOptions>),
         app,
         options);
 }
        public static IAppBuilder UseGitHubAuthentication(
            this IAppBuilder app, 
            string clientId,
            string clientSecret)
        {
            if (app == null)
            {
                throw new ArgumentNullException("app");
            }

            var option = new GitHubAuthenticationOptions(
                clientId,
                clientSecret)
            {
                SignInAsAuthenticationType = app.GetDefaultSignInAsAuthenticationType()
            };

            return UseGitHubAuthentication(app, option);
        }