This is not really an issue with the language but with the implemetnation and most languages/libraries/OS-es are not suited for "hard real-time" either.
How many people are writing "hard real-time" code? I suspect not many, and yes, for them probably Go is not the right tool at the moment, but also in great part because nobody has needed/wanted to use Go in such environments yet.
Requiring garbage collection is a language issue, not just an implementation issue. (Note that I do not think GC is a bad thing, but it matters a great deal in this context.) Making GC work in hard real-time system is a Hard Problem. I think you greatly underestimate how difficult it is, given your final sentence. Read the Metronome project I linked to.
You are correct that not many people write hard real-time code; it's generally found in such things as software controlling planes, power grids or power plants.
How many people are writing "hard real-time" code? I suspect not many, and yes, for them probably Go is not the right tool at the moment, but also in great part because nobody has needed/wanted to use Go in such environments yet.