Not too sure to be honest, there's no monster affix for treasure goblin. Would have to check via name; next time you find one press Dump RActors and post its name and id here and ill add it in.
In generic no there probably isnt.
Code:
if (unit.Name.StartsWith("treasureGoblin"))
{
Logger.WriteVerbose("Mob is a Treasure Goblin");
return true;
}