Non-zero exit code

Program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

internal static class Program
{
    public static async Task Main()
    {
        await new HostBuilder()
            .ConfigureServices(cfg => cfg.AddHostedService<ErrorBackgroundService>())
            .RunConsoleAsync();
    }

    internal sealed class ErrorBackgroundService : BackgroundService
    {
        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            // Yield here, because synchronously throwing ExecuteAsync calls
            // are handled by the host.
            await Task.Yield();
            try
            {
                Throw();
            }
            catch (OperationCanceledException oce) when (oce.CancellationToken == stoppingToken)
            {
                // This is fine, we threw because an operation got cancelled
                // because of shutdown.
            }
        }

        private void Throw()
        {
            throw new InvalidOperationException("This is deliberate");
        }

        public override async Task StopAsync(CancellationToken cancellationToken)
        {
            await base.StopAsync(cancellationToken);
            if (ExecuteTask?.IsFaulted == true && ExecuteTask.Exception is AggregateException aex)
            {
                // Throwing here is crucial to get a non-zero exit code
                throw new AggregateException($"{nameof(ErrorBackgroundService)} in fatal state", aex.InnerExceptions);
            }
        }
    }
}