- not such a constrained set of concurrency primitives
- such a basic type system.
I imagine those languages have a good type system and/or good concurrency primitives (i.e. possibly making up for their GC "penalty").
Actually the original Oberon type system is simpler than Go's. Its later revision Oberon-07 is even simpler.
All the other ones I mentioned, have better type systems than Go, even support for some form of generics.
Concurrency depends on the language, but you get a mix of threads, co-routines, tasks, active objects and processes, overall.