aspnetcore/samples/CookieSample/Startup.cs

using System.Linq;
using System.Security.Claims;
using Microsoft.AspNet.Authentication.Cookies;
using Microsoft.AspNet.Builder;
using Microsoft.AspNet.Hosting;
using Microsoft.AspNet.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace CookieSample
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddAuthentication();
        }

        public void Configure(IApplicationBuilder app, ILoggerFactory loggerfactory)
        {
            loggerfactory.AddConsole(LogLevel.Information);

            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AutomaticAuthenticate = true
            });

            app.Run(async context =>
            {
                if (!context.User.Identities.Any(identity => identity.IsAuthenticated))
                {
                    var user = new ClaimsPrincipal(new ClaimsIdentity(new[] { new Claim(ClaimTypes.Name, "bob") }, CookieAuthenticationDefaults.AuthenticationScheme));
                    await context.Authentication.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, user);

                    context.Response.ContentType = "text/plain";
                    await context.Response.WriteAsync("Hello First timer");
                    return;
                }

                context.Response.ContentType = "text/plain";
                await context.Response.WriteAsync("Hello old timer");
            });
        }

        public static void Main(string[] args)
        {
            var application = new WebApplicationBuilder()
                .UseConfiguration(WebApplicationConfiguration.GetDefault(args))
                .UseStartup<Startup>()
                .Build();

            application.Run();
        }
    }
}