It is in the original article [1], though I was made aware that Go implementation is also incorrect as `defer` in it make the memory usage to substantially raise. So instead of:

        defer wg.Done()
        time.Sleep(10 * time.Second)

In original article it should be:

        time.Sleep(10 * time.Second)
        wg.Done()

And memory usage will drop about 2x. I am no Go nor Java developer so I cannot say anything more.

[1]: https://pkolaczk.github.io/memory-consumption-of-async/

Heh Heh Heh, now do Python... ;)