As of right now, you should be able to stream HBO GO to your television through Apple TV. But you don't have an actual app with which to do it...yet.
What you can do is stream HBO GO to your television using Apple's AirPlay feature on your iPhone or iPad. All you have to do to begin beaming content from your smaller device to your TV is download the update to the HBO GO app on your device.
(You'll need iOS 6 or above and v5.1.1 or above on your Apple TV)
HBO's Eric Kessler made the announcement at the All Things D: Dive Into Media conference.
“Our long-term goal for Go is to be on all devices and all platforms,” said Kessler.
And you should expect to see an actual HBO GO app appear on Apple TV at some point.
"We will get on Apple TV, as we’ve said all along,” said Kessler.
Reports from earlier this month put a dedicated HBO GO app on Apple TV by mid-year.
HBO GO already has dedicated apps on devices like Roku and the Xbox 360., so Apple is lagging behind a little bit here. But at least the HBO GO app now supports AirPlay, which makes streaming possible. Go get your Game of Thrones on, people.