eShopOnContainers/src/Services/Payment/Payment.API/Program.cs

var configuration = GetConfiguration();

Log.Logger = CreateSerilogLogger(configuration);

try
{
    Log.Information("Configuring web host ({ApplicationContext})...", Program.AppName);
    var host = BuildWebHost(configuration, args);

    Log.Information("Starting web host ({ApplicationContext})...", Program.AppName);
    host.Run();

    return 0;
}
catch (Exception ex)
{
    Log.Fatal(ex, "Program terminated unexpectedly ({ApplicationContext})!", Program.AppName);
    return 1;
}
finally
{
    Log.CloseAndFlush();
}


IWebHost BuildWebHost(IConfiguration configuration, string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .CaptureStartupErrors(false)
        .ConfigureAppConfiguration(x => x.AddConfiguration(configuration))
        .UseStartup<Startup>()
        .UseContentRoot(Directory.GetCurrentDirectory())
        .UseSerilog()
        .Build();

Serilog.ILogger CreateSerilogLogger(IConfiguration configuration)
{
    var seqServerUrl = configuration["Serilog:SeqServerUrl"];
    var logstashUrl = configuration["Serilog:LogstashgUrl"];
    return new LoggerConfiguration()
        .MinimumLevel.Verbose()
        .Enrich.WithProperty("ApplicationContext", Program.AppName)
        .Enrich.FromLogContext()
        .WriteTo.Console()
        .WriteTo.Seq(string.IsNullOrWhiteSpace(seqServerUrl) ? "http://seq" : seqServerUrl)
        .WriteTo.Http(string.IsNullOrWhiteSpace(logstashUrl) ? "http://logstash:8080" : logstashUrl)
        .ReadFrom.Configuration(configuration)
        .CreateLogger();
}

IConfiguration GetConfiguration()
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
        .AddEnvironmentVariables();

    var config = builder.Build();

    if (config.GetValue<bool>("UseVault", false))
    {
        TokenCredential credential = new ClientSecretCredential(
            config["Vault:TenantId"],
            config["Vault:ClientId"],
            config["Vault:ClientSecret"]);
        builder.AddAzureKeyVault(new Uri($"https://{config["Vault:Name"]}.vault.azure.net/"), credential);
    }

    return builder.Build();
}

public partial class Program
{
    public static string Namespace = typeof(Startup).Namespace;
    public static string AppName = Namespace.Substring(Namespace.LastIndexOf('.', Namespace.LastIndexOf('.') - 1) + 1);
}