internal class Program
    {
        private static void Main(string[] args)
        {
            CreateHostBuilder(args)
                .Build()
                .Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureServices((hostBuilderContext, serviceCollection) =>
                {
                    IConfigurationSection myConfigurationSection = hostBuilderContext.Configuration.GetSection("app");

                    serviceCollection.AddSingleton<IValidateOptions<AppOptions>, AppOptionsValidator>();
                    serviceCollection.Configure<AppOptions>(myConfigurationSection);
                });
    }