using System;

using CommandLine;

​

class Options

{

    public Options(string option1)

    {

        Option1 = option1;

    }

    [Option('a', "option1", Required = true)]

    public string Option1 { get; init; }  // Commenting out "init;" makes the application run again

}

​

class Program

{

    static int Main(string[] args)

    {

        //set args manually.  If you need QUOTED args handling, you'll need to use a string[]

        args = "--option1 a".Split(' ');

        return Parser.Default.ParseArguments<Options>(args)

        .MapResult(

          options => RunAndReturnExitCode(options),

          _ => -1);

    }

​

    static int RunAndReturnExitCode(Options options)

    {

        Console.WriteLine($"option1={options.Option1}");

        return 0;

    }

}