Authentication and Authorization in ASP.NET Core 2

public void ConfigureServices(IServiceCollection services)
{
    // ...
    services.AddCors();
    services.AddSingleton<IWorkService, WorkService>();
    services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
        .AddCookie(o => o.LoginPath = new Microsoft.AspNetCore.Http.PathString("/login"))
        .AddGoogle(googleOptions =>
    {
        googleOptions.ClientId = Configuration["Authentication:Google:ClientId"];
        googleOptions.ClientSecret = Configuration["Authentication:Google:ClientSecret"];
    });
    services.AddAuthorization(options => {
        options.AddPolicy("authenticated", policy =>
        {
            policy.AuthenticationSchemes.Add(GoogleDefaults.AuthenticationScheme);
            policy.RequireAuthenticatedUser();
        });
    });
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILogger<Startup> logger, IConfiguration config)
{
    // ...
    app.UseAuthentication();
}