The Romanian stopper spent the last couple of days in talks with the Bundesliga outfit after deciding to quit Rangers.
Goian refused to join the first batch of players who called time on their Ibrox careers when they refused to have their contracts transferred over to the newco.
But the defender was finally forced to call time when SFL clubs voted Rangers into the Irn-Bru Third Division.
Goian immediately contacted manager Ally McCoist and owner Charles Green and informed them he couldn't afford to drop down the divisions.
Meanwhile, Rangers would have made former Caley Thistle striker Marius Niculae their first signing this summer – until they were dumped into the bottom tier.
They had pressed on with the hope of making several signings if they had been relegated just one division and their proposed transfer embargo had been overturned.
They had agreed a deal with Romanian striker Niculae, 31, who has been told he can leave Dinamo Bucharest in his homeland.
He shares the same agent as Goian, and Florin Manea said: "We had a very good offer for Marius from a European club. The talks were completed and the club would probably have surprised many people. But unfortunately, we could not proceed with the deal."
Niculae was a high-profile signing for Caley in 2007 and they paid him £4,000-a-week.