Program.cs

using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using System;

namespace Elect.Sample.DI
{
    public class Program
    {
        public static void Main(string[] args)
        {
            IWebHost webHost = BuildWebHost(args);

            OnAppStart(webHost);

            webHost.Run();
        }

        public static IWebHost BuildWebHost(string[] args)
        {
            var webHostBuilder = WebHost.CreateDefaultBuilder(args);

            webHostBuilder.UseStartup<Startup>();

            var webHost = webHostBuilder.Build();

            return webHost;
        }

        private static void OnAppStart(IWebHost webHost)
        {
            using (var scope = webHost.Services.CreateScope())
            {
                var serviceProvider = scope.ServiceProvider;

                var sampleService = serviceProvider.GetService<Startup.ISampleService>();

                var token = sampleService.GetRandomString();

                Console.WriteLine(token);
            }
        }
    }
}