Fast is relative to purpose. Maybe could afford to be faster in the context of an IDE checking your code on the fly, for a large project. I wouldn't know, since I have not attempted to write it.

actually, the Go tool compiles packages in parallel by default.

...under the assumption that something does not depend on too many cgo packages.

Source? That's not what the article says.

The 8g, 6g, etc compilers operate on a single .go file at a time. You're welcome to invoke them directly if you want.