Yeah, that makes the title pretty much clickbait, because a memory leak in a memory-safe language would really be a big deal...
It is not.
Let me show you a memory leak in the memory safe language, rust:
let vec: Vec<u8> = Vec::with_capacity(1024);
std::mem::forget(vec);
_ = time.Tick(1 * time.Second)
You can also, if you want to leak memory in go, set the environment variable GOGC=off, and there you go, instant memory leak.
Practically any language, memory safe or otherwise, will let you create a memory leak.
There are of course workarounds for this like reference counted wrappers and so on.
Although, it's pretty useless as an exploit, since it requires you to be able to run arbitrary Go code to begin with (the author admits as much). It's _very_ unlikely that a remote attacker could exploit a data race in a regular Go program.