app.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="8.0.1" />
  </ItemGroup>
</Project>

Program.cs

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

var builder = Host.CreateApplicationBuilder(args);

builder.Services.AddHostedService<PingWorker>();

var host = builder.Build();
await host.RunAsync();

public class PingWorker(ILogger<PingWorker> logger) : BackgroundService
{
    protected override Task ExecuteAsync(CancellationToken stoppingToken)
    {
        Timer timer = new (
            callback: (_) => logger.LogInformation($"This was generated at {DateTime.Now:R}"), 
            state: null, 
            dueTime: TimeSpan.Zero, 
            period: TimeSpan.FromSeconds(5)
        );
        return Task.CompletedTask;
    }
}