I would argue that Go has it more "baked in."

But I'm actually curious as well. Given that Objective-C (and now Swift) have GCD, what language features are needed to bring concurrency up to par with Go?

I'm sort of reminded of what Microsoft did after Task Parallel Library came out with C#. People didn't pay attention too much to what MS was building until async/await came out (along with tooling support). But async/await built upon TPL. So it's probably a matter of time for Apple to do something similar on top of GCD, if they're going to do something. But I doubt it's going to look something like Go.

Go provides straight-ahead, blocking-is-OK concurrency. GCD provides callback-based concurrency, like node.js, but with several worker threads instead of just one.