Program.cs

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Serilog;
using Serilog.Sinks.Elasticsearch;
using System.Reflection;

namespace Webapi_Serilog
{
    public class Program
    {
        public static void Main(string[] args)
        {
            ConfigureLogging();

            CreateHost(args);
        }

        private static void ConfigureLogging()
        {
            var environment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
            var configuration = new ConfigurationBuilder()
                .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
                .AddJsonFile(
                    $"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")}.json",
                    optional: true)
                .Build();

            Log.Logger = new LoggerConfiguration()
                .Enrich.FromLogContext()
                .Enrich.WithMachineName()
                .WriteTo.Debug()
                .WriteTo.Console()
                .WriteTo.Elasticsearch(ConfigureElasticSink(configuration, environment))
                .Enrich.WithProperty("Environment", environment)
                .ReadFrom.Configuration(configuration)
                .CreateLogger();
        }

        private static ElasticsearchSinkOptions ConfigureElasticSink(IConfigurationRoot configuration, string environment)
        {
            return new ElasticsearchSinkOptions(new Uri(configuration["ElasticConfiguration:Uri"]))
            {
                AutoRegisterTemplate = true,
                IndexFormat = $"{Assembly.GetExecutingAssembly().GetName().Name.ToLower()}-{environment?.ToLower().Replace(".", "-")}-{DateTime.UtcNow:yyyy-MM}"
            };
        }
        private static void CreateHost(string[] args)
        {
            try
            {
                CreateHostBuilder(args).Build().Run();
            }
            catch (System.Exception ex)
            {
                Log.Fatal($"Start Failed! {Assembly.GetExecutingAssembly().GetName().Name}", ex);
                throw;
            }
        }


        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                })
                .ConfigureAppConfiguration(configuration =>
                {
                    configuration.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
                    configuration.AddJsonFile(
                        $"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")}.json",
                        optional: true);
                })
                .UseSerilog();
    }
}