private static IResult <string, int> GetChoice(FeatureMap featureMap)
{
var choice = Console.ReadLine();
return(!Int32.TryParse(choice, out int x)
? Result.Failure <string, int>("Couldn't parse " + choice + " as an integer")
: featureMap.DoesFeatureExist(x) ?
Result.Success <string, int>(x)
: Result.Failure <string, int>("Don't know the feature for choice #" + x));
}