The much-travelled 34-year-old former Chelsea goalkeeper recently had a trial at League Two outfit Bradford, but failed to win a deal at Valley Parade.
"It's a huge challenge which I'm really looking forward to," Colgan told the club's official website.
"I got the call from the gaffer and he gave me 24 hours to think about it, but I think it took me about 24 seconds to decide!
"He told me he wants to carry a good squad of goalkeepers and it's my job to bring my experience to the other keepers and to add some pressure on them and keep them on their toes, and I'm looking forward to getting started."




