No thread/goroutine handles for fork/join handling from "outside", and no generics for many formative years that influenced tons of habits, then significantly weaker generics (improving very soon[1]), have all led to most concurrent code to be very "intrusive" - you create bare threads and add bare synchronization primitives (or nearly) by hand inside the threaded code to make it concurrent. `errgroup` is as far as a lot of code goes, in terms of sophistication.

Java leans heavily in the other direction: a lot of concurrency is added externally, without changing existing code, often in very declarative-flavored ways.

E.g. Future<T> serves as a foundation for a ridiculous amount of stuff, while Go forces channels for `select` whether they model your problem nicely or not, and they're very difficult (often impossible) to wrap without changing semantics.

There are very obviously lots of counter-examples for both langs (`synchronized`, rill in Go, etc), and I expect Go to become more Java-flavored in time (it already has moved this direction somewhat, and 1.27 will enable a lot more). But I think it's a fair summary of broad ecosystem habits.

1: https://tip.golang.org/doc/go1.27 (not yet released)