Simple console application (Generic Host)

appsettings.json

{
  "Messages": {
    "Salutation": "Hello"
  }
}

console.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net9.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Hosting" Version="*" />
  </ItemGroup>
</Project>

Program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Hosting.Internal;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);

builder.Services.AddSingleton<IHostLifetime, ConsoleLifetime>();
builder.Services.AddScoped<IMessageService, MessageService>();
builder.Services.Configure<Messages>(builder.Configuration.GetSection(nameof(Messages)));
builder.Services.AddSingleton<string[]>((_) => args);
builder.Services.AddHostedService<ConsoleWorkerService>();

IHost host = builder.Build();

await host.RunAsync();

internal record Messages
{
    required public string Salutation { get; init; } = "Hello";
}

internal interface IMessageService
{
    string GetMessage();
}

internal class MessageService(
    IOptions<Messages> messagesOptions,
    string[] arguments
) : IMessageService
{
    private readonly Messages messages = messagesOptions.Value;

    public string GetMessage() => $"{messages.Salutation}, {arguments.FirstOrDefault() ?? "World"}!";
}

internal class ConsoleWorkerService(
    IMessageService messageService,
    ILogger<ConsoleWorkerService> logger,
    IHostApplicationLifetime hostApplicationLifetime
) : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        await Task.Delay(TimeSpan.FromSeconds(1), stoppingToken);
        string message = messageService.GetMessage();
        logger.LogInformation(message);
        hostApplicationLifetime.StopApplication();
    }
}

Properties__launchSettings.json

{
  "profiles": {
    "console": {
      "commandName": "Project",
      "environmentVariables": {
        "DOTNET_ENVIRONMENT": "Development"
      }
    }
  }
}