Contract expiration dates:
2017 - Stephan Lichtsteiner, Patrice Evra (+1 option), Paolo De Ceglie
2018 - Gianluigi Buffon, Andrea Barzagli, Giorgio Chiellini, Kwadwo Asamoah, Hernanes, Massimiliano Allegri, Dani Alves, Mehdi Benatia (loan)
2019 - Neto, Sami Khedira, Mario Mandzukic, Juan Cuadrado (loan), Federico Mattiello
2020 - Leonardo Bonucci, Alex Sandro, Claudio Marchisio, Paulo Dybala, Mario Lemina, Rolando Mandragora, Emil Audero
2021 - Gonzalo Higuaín, Marko Pjaca, Miralem Pjanić, Daniele Rugani, Stefano Sturaro
I think this is up to date. Any corrections let me know.