The "tú" is optional, as subject pronouns generally are in Spanish. The general advice to language learners is to get used to leaving them out unless there's a specific reason to include them (ambiguity, contrast, emphasis).
You would include "tú" only if you have previously specified where are yourself (or any other person) going to go. "Yo voy a... ¿adónde vas tú?" "Juan va a Santander, ¿adónde vas a ir tú el domingo?"
In other case, if you include "tú", you are giving the impression that you are going to say where are you (or any other person) going to go. "¿Adónde vas a ir tú el domingo? [you answer]... Yo, a ver a mi madre".