Let me put it another way: Go's GC is still in its infancy compared to those in most other languages. It's perfectly fine to use, but there are some big things (e.g. no compaction) that stick out when using the language, whether you're working with free-lists or something else.
That's a dicier assertion to make versus other languages, notably Java, but if you're coming to Golang from a high level language like Python, you're probably going to be happy with the performance you get out of naive code.
I love Go, but "it's fast" isn't a good reason not to improve a subpar GC. (Which fortunately isn't a position the Go team is taking. I know everyone there would like to see a lot of interesting things happen with the GC. It just hasn't been one of the more pressing issues so far, and I've agreed. It's also a very difficult and "boring" thing to work on for most people, so it's not surprising that somebody hasn't just added an Azul C4-style concurrent GC in their spare time.)
Java HotSpot's collector makes the most sense IMHO: stop the world compacting in the young generation, mostly concurrent in the tenured generation. It achieves better throughput than Azul C4 too, according to the C4 paper.
A while ago, I read through the kernel patch they provided, and it was basically adding batch APIs for mremap so you don't have to have a TLB flush for every call. Also because all mutator threads needed to be paused at a safepoint while the remaps happen, so the batch API has much shorter pause time.
I would pay throughput to achieve (soft) real-time GC.
The problem with GC's languages, is that GC is "good enough" for prototyping and for undemanding stuff, but there are still these corner cases. Really, it's no different than other forms of memory management in this regard. It's just particularly beginner friendly.
If I recall correctly, there are still some very strong warnings against running Go on memory-constrained systems (< 1 GB).
However, if performance is a concern, then picking Go seems to me like quite a step back from say Ruby.
There are other alternatives as well, that are higher level and that are much better at performance than Ruby/Python. E.g. Java, C#, Scala, Clojure, Ocaml, Haskell.
Personally I love Scala and the JVM, but the one thing I don't like is the GC. The JVM has the best GCs ever, but sometimes you just want to do without one at all.
This is why I don't like Go. While it's a tasteful language, it's too low level, but it still depends on a GC (that's not precise, compacting or generational).
Mozilla's Rust is much more promising for me.