[cies]

I agree. It feels a bit like where Java/JVM is at: popular, solid runtime, large community/ecosystem, but Java made some bad choices.

In my opinion: Go needs a Kotlin. First and foremost to do away with implicit nulls (imho the biggest mistake), but here are other things that could be impoved you've already mentioned.

[seer-zig]

The good thing is that Java is incorporating the proven features of other languages. It has gotten records, pattern matching (better than Kotlin's), and in the latest release, virtual threads with structured concurrency, better than async/await, and also better than golang as it lacks structured concurrency.

[cies]

But implicit nulls are a big pain point (in both Java and Go). And its very hard to fix for Java (and no plant thus far).

[seer-zig]

There are solutions like CheckerFramework or Nullaway or other compile time annotation processors.

[cies]

...and Kotlin :)