Attempting to configure services in the DI container based on command line parameters with System.CommandLine... and failing miserably

example.cs

namespace test {
    interface IFooBar
    {
        public string Foo { get; init; }
        public int Bar { get; init; }
    }

    public class FooBar
        : IFooBar
    {
        public FooBar(string f, int b)
        {
            Foo = f;
            Bar = b;
        }

        public string Foo { get; init; }
        public int Bar { get; init; }
    }

    class Program
    {
        private class SomeOptions
        {
            public string Foo { get; set; }
            public int Bar { get; set; }
        }

        static async Task<int> Main(string[] args)
        {
            var root =
                new RootCommand("Foo bar")
                {
                    new Option<string>(
                        new[] {"-f", "--foo"},
                        description: "foo"
                    ) {IsRequired = true},
                    new Option<int>(
                        new[] {"-b", "--bar"},
                        description: "bar"
                    ) {IsRequired = true}
                };

            root.Handler = CommandHandler.Create<IHost>(host =>
            {
                var opts = host.Services.GetRequiredService<IOptions<SomeOptions>>();

                Console.WriteLine($"opts: {opts.Value.Bar} - {opts.Value.Foo}");

                var foo = host.Services.GetRequiredService<IFooBar>();
                Console.WriteLine($"foo: {foo.Bar} - {foo.Foo}");

                // var f = host.Services.GetRequiredService<IFooBar>();
                // Console.WriteLine($"{f.Bar} - {f.Foo}");
            });

            var parser = new CommandLineBuilder(
                    root
                )
                .UseHost(host =>
                {
                    host.ConfigureServices(services =>
                    {
                        services.AddOptions<SomeOptions>().BindCommandLine().Configure<ParseResult>((o, r) =>
                        {
                            Console.WriteLine("Configuring...");
                            services.AddSingleton<IFooBar>(new FooBar(o.Foo, o.Bar));
                        });
                    });
                })
                .Build();

            return await parser.InvokeAsync(args);
        }
    }
  }

Results in the following output:

Configuring...
opts: 1234 - hello

Followed by a crash as the call to host.Services.GetRequiredService() failed to resolve the registered dependency. :\