In a large pot of water, bring some water to a boil. Add the pasta and cook until al dente. Drain the noodles and pour them into a large mixing bowl. Set aside to cool. Dice the carrots, celery and onions into small pieces. Add the vegetables to the pasta. Add the mayo, milk, sugar, vinegar and salt & pepper. Season with more or less mayo as needed. Add a few dashes of Sriracha to add a little kick if you'd like. Keep in the fridge until cold.