MyApp.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Hosting" Version="5.0.0" />
  </ItemGroup>

</Project>

Program.cs

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

// Create the generic host for my application.
IHost app = Host
    .CreateDefaultBuilder(args)
    .ConfigureServices(ConfigureServices)
    .Build();

// Use the dependency injection to grab my command handler and run it.
MyCommand command = app.Services.GetRequiredService<MyCommand>();

command.Run();

// Prepare my dependency injection container.
void ConfigureServices(HostBuilderContext context, IServiceCollection services)
{
    services.AddSingleton<MyCommand>();
}

public class MyCommand
{
    public void Run()
    {
        Console.WriteLine("Hello");
    }
}