You also don’t make that choice until your creature is actually entering. Let’s say you cast the Goblin, and your opponent has a Shock and a counterspell. They want to counter your Goblin if you plan to make it a 3/3, but they’ll just Shock it if you want to swing with a hasty 2/2; so, they ask “+1/+1 or Haste?”, regarding Riot. You don’t have to answer that! It’s a choice you don’t have to make just yet. You can just tell your opponent “I make that choice as this spell resolves. Does it resolve?”, and that’s what I’d recommend at FNM. You also have the ‘meaner’ option: by asking you about a choice you don’t make until this spell resolves, your opponent is assumed to have proposed a shortcut wherein they are passing priority and letting the spell resolve. You can technically make your choice here and they lose their chance to resolve to your spell. Personally, I’d recommend holding onto that line of play for Competitive events- at Regular Rules Enforcement events like FNM, do the ‘nice’ thing and just let them know you don’t have to make that choice yet.
All of this hinkiness is specifically because Riot is a replacement effect that modifies how the creature enters. If it were a trigger, then your Goblin would come down as an unhasted 2/2, and your opponent could Shock it with the trigger on the stack. Also, since it’s not a trigger, it totally dodges things like Tocatli Honor Guard! It does also mean that if you’re playing some insane Temur pile with Naban, Dean of Iteration and Rhythm of the Wild for Rioting Wizards, Naban won’t let you double-riot. Your Wizards are too orderly for that! Until you play a second copy of Rhythm, anyway- then you can Double Riot all day long, because multiple instances of Riot are NOT redundant! Make all your creatures come in +2/+2 bigger, or +1/+1 bigger with haste. Happy Smashing!
Today’s Gruuls Tip was written by Trevor Nunez