Not all Java implementations map language threads to OS threads.

The implementations that use green threads are no different than go-routines, which were seen for the first time in Modula-2 just as information.

What I was implying is that "built for concurrency" isn't just about threads (or goroutines). It's about communication between concurrent routines and shared state. Go is designed to have less coordination in concurrency by encouraging communication via channels instead of shared state.