In this context (I see you Lispers) the difficulty of adding a new keyword to the compiler is less a property of the language than a property of how the compiler's implemented.

Specifically, the weird stuff the author encountered like:

* Generating the token list by parsing the comments of a source file

* only parsing up to a hard-coded token instead of all of the known tokens (?!)

* using a hacky token hashing mechanism that only looks at the first two characters of the token

have nothing to do with Go-the-language.