using System;

using System.IO;

using System.Linq;

using Microsoft.Extensions.Logging;     

using Microsoft.Extensions.DependencyInjection; 

using Microsoft.Extensions.Configuration;

using Microsoft.Extensions.Configuration.Json;

using Microsoft.Extensions.Hosting;

using System.Threading;

using System.Threading.Tasks;

using System.Reflection;

​

public class Program

{

    public static async Task Main(string[] args)

    {

        var config = new ConfigurationBuilder()

                        .AddJsonFile("appsettings.json", optional: true)

                        .AddInMemoryCollection()

                        .Build();

        config["HostedServices"] = "worker1";

        var hostBuilder = Host.CreateDefaultBuilder(args)

            .ConfigureServices((hostContext, services) =>

            {

                var workersString = config.GetValue<string>("HostedServices");

                var workers = workersString.Split(",");

                if(workers.Contains("worker1"))

                {

                    services.AddHostedService<Worker1>();

                }

                if(workers.Contains("worker2"))

                {

                    services.AddHostedService<Worker2>();

                }

            }).ConfigureLogging(b => {

                b.AddConsole();

                b.SetMinimumLevel(LogLevel.Information);

            });

        using(var host = hostBuilder.Build())

        {

            await host.StartAsync();

            await host.StopAsync();

        }

    }

    public class Worker1 : IHostedService 

    {

        ILogger _logger;

​

        public Worker1(ILogger<Worker1> logger)

        {

            _logger = logger;

        }

        public Task StartAsync (CancellationToken cancellationToken)

        {

            _logger.LogInformation("Started: worker1");

            return Task.CompletedTask;

        }

        public Task StopAsync (CancellationToken cancellationToken)

        {

            _logger.LogInformation("Stopped: worker1");

            return Task.CompletedTask;

        }

    }

    public class Worker2 : IHostedService 

    {

        ILogger _logger;

​

        public Worker2(ILogger<Worker2> logger)

        {

            _logger = logger;

        }

        public Task StartAsync (CancellationToken cancellationToken)

        {

            _logger.LogInformation("Started: worker2");

            return Task.CompletedTask;

        }

        public Task StopAsync (CancellationToken cancellationToken)

        {

            _logger.LogInformation("Stopped: worker2");

            return Task.CompletedTask;

        }

    }

}