Consuming transient services from singletons

Startup.cs

public class BarService
{
    public DateTime Now { get; } = DateTime.UtcNow;
}

public class FooService
{
    private readonly BarService _barService;

    public FooService(BarService barService)
    {
        _barService = barService;
    }

    public string PrintDate() => _barService.Now.ToString("dd-MM-yyyy HH:mm:ss:ffff");
}

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<FooService>();

        // This turns BarService into a singleton
        services.AddTransient<BarService>();

        // This would cause resolving FooService to throw an exception (as expected)
        //services.AddScoped<BarService>();
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        app.Run(async (context) =>
        {
            try
            {
                var fooService = context.RequestServices.GetRequiredService<FooService>();
                await context.Response.WriteAsync("Hello World: " + fooService.PrintDate());
            }
            catch (Exception ex)
            {
                await context.Response.WriteAsync(ex.ToString());
            }
        });
    }
}