With cgo, Go can get "just as close" to the metal too. But I don't even think a cgo vs. JNI benchmark would be substantive. Most people don't use a "medium-"level programming language to write low-level code, anyway.
Like you say, Java is barely less verbose and arguably just as powerful as Go with many more times over the documentation and resources.
Oh, I would say Java is much, much more powerful than Go. Other than dynamic code loading and runtime instrumentation, even when it comes to concurrency you have your choice of schedulers and control over OS threads.
Like you say, Java is barely less verbose and arguably just as powerful as Go with many more times over the documentation and resources.