The game should not have ended.

That's a totally illogical move. FIDE needs to fix this

The rook is pinned alright! But it's the queen that checkmated you

But I can just capture the queen since the rook is pinned, it can't be able to move. That's a bs move.

 No you can't, with whatt? Kg1 is an illegal move, since you can't put your king in check! Although the rook is pinned it can still check the king i.e a dicovered check.

The pinned rook can not move but it still projects its power down the open file protecting the queen giving mate.

Imagine the rook having archers shooting along the g-file. When the king takes the queen, the king gets shot and dies.

How come people are still responding to trolls?

Yes, you are correct, the rook on g6 was pinned. But, just because it's pinned, does not mean it still doesn't protect that g file. So even though it's pinned, it protects the queen when it moves to g1#. The queen could have moved to g2, and it would still be #. Please go over the game again knowing this. As the others have said, the rook is pinned but it still functions and it can still protect the queen for mate. 

-blitz

I think the easiest way to understand it is that you are trying to kill his king before he kills yours. If Kxg1 the rook would have killed your king before your queen could behead his king. It would have been a close one but your king would have died first.

This is one of the reasons why I say a game should end with capturing the king rather than checkmate.

Nah..if you're in checkmate, the next move will probably involve the capturing of the king so that would just be a waste.

But someone might miss a hanging king!

No, it's totally logical. You are the one being inconsistent essentially saying "white can expose his king to check, because black isn't allowed to expose his king to check."

If that's too confusing for you, sometimes it helps to point out which king would be captured first.

exactly