public async System.Threading.Tasks.Task <ActionResult> LogOutAsync()
        {
            var cp          = (ClaimsPrincipal)User;
            var idtokenHint = cp.FindFirst("id_token");

            if (idtokenHint != null)
            {
                var client = new HttpClient();
                var disco  = await client.GetDiscoveryDocumentAsync(new DiscoveryDocumentRequest()
                {
                    Address = "http://localhost:5000",
                    Policy  = { RequireHttps = false }
                });

                var ru         = new IdentityModel.Client.RequestUrl(disco.EndSessionEndpoint);
                var endsession = ru.CreateEndSessionUrl(idtokenHint.Value, postLogoutRedirectUri: "http://localhost:5001/signout-oidc");
                return(Redirect(endsession));
            }
            return(RedirectToAction("SsoSignOutCallBack", "Home"));
        }