Nope. It's random. However, here are ways to get a Brave Nature you want on Golurk:
Breeding With Everstone.
If a parent holds an Everstone, then there is a 100% chance that the mother's nature will be passed down to the baby Golett. Source.
wtf is that le scratchpost
A Pokemon with Synchronize placed in Party Slot 1, such as Abra, the chance of encountering a wild Pokemon with the same nature as Abra will be 50%. So, if you catch a Pokemon with Synchronize with a Brave Nature, put that in your lead slot and you have that higher chance.
Source: Experience and above links.