Program.cs

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Serilog;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;

namespace ExcelUpload
{
    public class Program
    {
        public static IConfiguration Configuration { get; } = new ConfigurationBuilder()
             .SetBasePath(Directory.GetCurrentDirectory())
             .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
             .AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Production"}.json", optional: true)
             .AddEnvironmentVariables()
             .Build();

        public static void Main(string[] args)
        {
            Log.Logger = new LoggerConfiguration()
               .ReadFrom.Configuration(Configuration)
               .Enrich.FromLogContext()
               .WriteTo.Debug()
               .CreateLogger();

            try
            {
                Log.Information("Starting web host");
                Log.Information("Application version {Version} starting up",
                    typeof(Program).Assembly.GetName().Version);

                CreateHostBuilder(args).Build().Run();

                Log.Information("Stopping web host");
            }
            catch (Exception ex)
            {
                Log.Fatal(ex, "Host terminated unexpectedly");
            }
            finally
            {
                Log.CloseAndFlush();
            }           
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .UseSerilog()
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}