The Argentina joins on an €8m loan from Fiorentina, with an option to buy for €33m, including bonuses.
“I’m very happy to be here wearing this shirt. It was a dream for me and my family. I’m so happy, I can’t really say anything else,” Gonzalez said.
“When you are young, you have to dream big. Getting to this team means everything to me. I can’t wait to get on the pitch and play with the team.
“I came here to win, there are no other words. Win, or win. I will do everything I can to help win every game.”
Gonzalez will again call ex-Fiorentina striker Dusan Vlahovic a teammate.
“I know him and he knows me, but we haven’t spoken much recently, he didn’t want to get anyone in any trouble. We had to wait for the right moment to see what would actually happen. I can’t wait to see him in the dressing room, though.
“I will do everything I can to win every match. I will always give 100% until the end.”