graceful-shutdown-host.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Threading;
using System.Threading.Tasks;

var host = new HostBuilder()
    .ConfigureServices((hostContext, services) => services.AddHostedService<ShutdownService>())
    .UseConsoleLifetime()
    .Build();

await host.RunAsync();

class ShutdownService : IHostedService
{
    private bool pleaseStop;
    private Task BackgroundTask;
    private readonly IHostApplicationLifetime applicationLifetime;

    public ShutdownService(IHostApplicationLifetime applicationLifetime)
    {
        this.applicationLifetime = applicationLifetime;
    }

    public Task StartAsync(CancellationToken _)
    {
        Console.WriteLine("Starting service");

        BackgroundTask = Task.Run(async () =>
        {
            while (!pleaseStop)
            {
                await Task.Delay(50);
            }

            Console.WriteLine("Background task gracefully stopped");
        });

        return Task.CompletedTask;
    }

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        Console.WriteLine("Stopping service");

        pleaseStop = true;
        await BackgroundTask;

        Console.WriteLine("Service stopped");
    }
}