abp/templates/console/src/MyCompanyName.MyProjectName/HelloWorldService.cs

using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using Volo.Abp.DependencyInjection;

namespace MyCompanyName.MyProjectName;

public class HelloWorldService : ITransientDependency
{
    public ILogger<HelloWorldService> Logger { get; set; }

    public HelloWorldService()
    {
        Logger = NullLogger<HelloWorldService>.Instance;
    }

    public Task SayHelloAsync()
    {
        Logger.LogInformation("Hello World!");
        return Task.CompletedTask;
    }
}