GSS.Authentication.CAS - How to logout Microsoft .NET6 APIs from CAS

Question

I have integrated the CAS protocol authentication in my solution, using the GSS.Authentication.CAS library. I created an Account controller and a Login API and the authentication works fine.

Now I would like to manage the logout from my APIs and from CAS, but if I do something like the following nothing happens.

In the Account controller I have:

[AllowAnonymous]
 [Route("Logout")]
 [HttpGet()]
 public IActionResult Logout()
 {
     return SignOut(CookieAuthenticationDefaults.AuthenticationScheme);
 }

In program.cs I have standard code like:

 .AddCookie(options =>
 {
     options.Events.OnSigningOut = context =>
     {
         Log.Information($"OnSigningOut called");
         
         var redirectContext = new RedirectContext<CookieAuthenticationOptions>(
             context.HttpContext,
             context.Scheme,
             context.Options,
             context.Properties,
             "/"
         );
         if (builder.Configuration.GetValue("Authentication:CAS:SingleSignOut", false))
         {
             Log.Information($"Executing SingleSignOut");

             // Single Sign-Out
             var casUrl = new Uri(builder.Configuration["Authentication:CAS:ServerUrlBase"]);
             var links = context.HttpContext.RequestServices.GetRequiredService<LinkGenerator>();
             var serviceUrl = context.Properties.RedirectUri ?? links.GetUriByPage(context.HttpContext, "/Index");
             redirectContext.RedirectUri = UriHelper.BuildAbsolute(
                 casUrl.Scheme,
                 new HostString(casUrl.Host, casUrl.Port),
                 casUrl.LocalPath, "/logout",
                 QueryString.Create("service", serviceUrl!));
         }

         context.Options.Events.RedirectToLogout(redirectContext);
         return Task.CompletedTask;
     };
 })

I was expecting to see the OnSigningOut event triggered, but this does not happen.

Do you have any idea where I'm wrong?

Thank you