This is a puzzling decision on Discord's part, because they found the single line of code causing their problem and they didn't think to change that line of code for their own needs. Go distributions include the source for Go itself, so building your own Go binary with your own changes incorporated is dead easy. And, the change they needed is a single-line change, which means it's easy to bring that change forward as new versions of Go are released.

Discord: haha, no, that's silly! let's spend 100,000x more effort and rewrite it all in another language!

Now, before those of you who learned to argue on the internet extrapolate what I wrote and imagine that I wrote words I didn't write: I'm not saying that Go should never be abandoned for another language. I'm saying that this particular example of this particular choice puzzles me, because of the reasons stated, and ONLY the reasons stated.

That's not what the article is saying.

It describes a rewrite of a single service from Go to Rust.

Reading between the lines, a rather simple piece of code.

At no point it implies that Discord rewrote all their Go code in Rust and completely abandoned Go.