using System;

using System.Collections.Generic;

using System.Threading.Tasks;

using System.Threading;

using Microsoft.Extensions.Logging;

using Microsoft.Extensions.Hosting;

using Microsoft.Extensions.Configuration;

using Microsoft.Extensions.DependencyInjection;

​

public class Program

{

    public static async Task Main()

    {

        TestSetEnv(new Dictionary<string, string> 

        { 

            { "test", "test" }

        });

        var host = CreateHostBuilder(new string[0]);

        await host.RunConsoleAsync();

    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>

            Host.CreateDefaultBuilder(args)

                 .ConfigureServices(services => services.AddHostedService<ConfigurationReader>())

                 .ConfigureAppConfiguration((hostingContext, config) =>

                 {

                     config.AddEnvironmentVariables();

                 })

                 .ConfigureLogging(b => b.AddConsole());

    public static void TestSetEnv(IDictionary<string, string> configurationList)

    {

        foreach (var cfg in configurationList)

        {

            Environment.SetEnvironmentVariable(cfg.Key, cfg.Value, EnvironmentVariableTarget.Process);

        }

    }

    public class ConfigurationReader: IHostedService 

    {

        private readonly ILogger _logger;

        private readonly IConfiguration _configuration;

        public ConfigurationReader(IConfiguration configuration, ILogger<ConfigurationReader> logger) 

        {

            _configuration = configuration;

            _logger = logger;

        }

        public Task StartAsync(CancellationToken token) 

        {

            var items = _configuration.AsEnumerable();

            foreach(var item in items)

            {

                _logger.LogInformation("{0}: {1}", item.Key, item.Value);

            }

            return Task.CompletedTask;

        }

        public Task StopAsync(CancellationToken token) 

        {

            return Task.CompletedTask;

        }

    }

}