Rangers centre-back Goldson played with the 28-year-old Republic of Ireland international central defender at Brighton, and the 27-year-old has responded to his post on Instagram.
Goldson responded: “Does the contract have a 14 day cancellation period?”
Is Shane Duffy a good signing for Celtic?
Duffy is a very good and strong central defender who has extensive experience, and that will come in handy for Celtic this season.
The 28-year-old struggled for playing time at the Seagulls last season, but he remains a player on top of his game who will make an immediate impact at Celtic.
Neil Lennon’s side have struggled defensively this season, and the arrival of Duffy will make things better.
Rangers are at the top of the Scottish Premiership table at the moment with 16 points from six matches, while Celtic currently find themselves third in the standings with 10 points from four games.
The Hoops are aiming to make it 10 league titles in a row this season, but the Gers will be determined to stop their Old Firm rivals from doing that.