- Direct memory access through `unsafe`. Python kinda does through `ctypes`?
- Tightly integrated assembly language; just pop Go-flavored assembly into your package and you can link directly to it.
- Statically-compiled code with AOT; no bytecode, no interpreters, no JITs.
Therefore what really sets Go apart is that it gives you all of these rich standard library capabilities in a relatively lower level language.
Of course I kind of understand why Rust and C++ don't put e.g. a PNG decoder in the standard library, I think this is somewhat an issue of mentality; those are things that are firmly the job of libraries. But honestly, I wish they did. It's not like the existence of things in the standard library prevents anyone from writing their own versions (It doesn't stop people from doing so in Go, after all), but when done well it provides a ton of value. I think nobody would claim that Go's flags library is the best CLI flag parsing library available. In fact, it's basically just... fine. But, on the other hand, it's certainly good enough for the vast majority of small utilities, meaning that you can just use it whenever you need something like that, and that's amazing. I would love to have that in Rust and C++.
And after experiencing OpenSSL yet again just recently, I can say with certainty that I'd love Go's crypto and TLS stack just about everywhere else, too. (Or at least something comparable, and in fairness, the rustls API looks totally fine.)