aspnetcore-cookie-authentication.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
    .AddCookie(CookieAuthenticationDefaults.AuthenticationScheme, o => { o.LoginPath = "/login"; });

builder.Services.AddAuthorization();

var app = builder.Build();

app.UseAuthentication();
app.UseAuthorization();

app.MapGet("/login", async (context) =>
{
    var claimsIdentity = new ClaimsIdentity(
        new[] { new Claim(ClaimTypes.Email, "email@example.com") },
        CookieAuthenticationDefaults.AuthenticationScheme
    );
    await context.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme,
        new ClaimsPrincipal(claimsIdentity)
    );
    await context.Response.CompleteAsync();
});

app.MapGet("/", () => "Hello World!").RequireAuthorization();

app.Run();