Enter the Tower of Challenges mode and reach challenge 150, called Autograph for whom? (in the original, Gor-owned ), where you will control the shokan against five opponents, one behind the other. Goro can not be controlled in any other Mortal Kombat mode 9.
Mortal Kombat 9 (2011): How to Play as Goro
In Mortal Kombat 9 for the PS3 and Xbox 360, Goro & Kintaro are not currently playable characters in the regular modes. They may be made as DLC characters at some point, but it is unknown at this time if they will be or not.
You can however play as Goro in the challenge tower. Choose challenge number 150 in the challenge tower and you will play as Goro, requiring you to defeat five enemies in a row without dying.
Check out his moves list, and make sure to try out his devastating X-Ray attack. You can replay challenges in the challenge tower as many times as you want as well.
How to unlock Mk 9 Goro