public static class ServiceCollectionExtensions
{
    public static TSettings AddConfig<TSettings>(this IServiceCollection services, IConfiguration configuration)
        where TSettings : class, new()
    {
        return services.AddConfig<TSettings>(configuration, options => { });
    }

    public static TSettings AddConfig<TSettings>(this IServiceCollection services, IConfiguration configuration, Action<BinderOptions> configureOptions)
        where TSettings : class, new()
    {
        if (services == null) { throw new ArgumentNullException(nameof(services)); }
        if (configuration == null) { throw new ArgumentNullException(nameof(configuration)); }
        TSettings setting = configuration.Get<TSettings>(configureOptions);
        services.TryAddSingleton(setting);
        return setting;
    }
}