public void ConfigureServices(IServiceCollection services)
    {
        services.AddAuthentication()
            .AddSaml2(options =>
            {
                options.SPOptions.EntityId = new EntityId("https://localhost:3131/Saml2");
                options.IdentityProviders.Add(
                    new IdentityProvider(
                        new EntityId("http://localhost:52071/Metadata"), options.SPOptions)
                    {
                        LoadMetadata = true
                    });

                options.SPOptions.ServiceCertificates.Add(new X509Certificate2("Sustainsys.Saml2.Tests.pfx"));
            });
    }

public class SsoController : Controller
{
    private CustomSaml2Handler _customSaml2Handler;
    public SingleSignOnController(CustomSaml2Handler customSaml2Handler)
    {
        _customSaml2Handler = customSaml2Handler;
    }

    [Route("saml2/ACS")]
    [HttpPost]
    public ActionResult ACS()
    {
        try
        {
         // How I should call HandleRequestAsync ?
        // How to get principals/claims?
        }
        catch (Exception e)
        {

        }
    }
}