There doesn't seem to be a way to pass. How do you end the game?

As a very bad Go player, the bot managed to be even worse than me in several key engagements, giving me territory I had no right to capture. It still beat me by a little bit, though (I think -- the game never actually ended!) I wonder if complementing the NN with a more traditional tree search would help it play better tactically.

EDIT: Also, your paper link is broken for me: replacing https:// with http:// makes it work.