ConfigurationBuilder.cs

var configurationBuilder = new ConfigurationBuilder()
    .SetBasePath(Path.Combine(HttpRuntime.AppDomainAppPath, "configs"))
    .AddJsonFile("settings.json", optional: false);
var configuration = configurationBuilder.Build();
var builder = new ContainerBuilder();
builder.RegisterOptions();
builder.RegisterConfigurationOptions<MailingOptions>(configuration.GetSection("mailing"));
builder.RegisterConfigurationOptions<FeedOptions>(configuration.GetSection("feed"));