I guess the argument is "I already know Go" (or Python etc.). But you probably already know json (yaml), too. And if not, it won't take long to learn.
I go farther, all told. I think any sort of diagram should almost certainly be process/pipeline based. Parts can be generated by a declarative markup, certainly. But you need a pipeline to "hand tune" things or you will end with diagrams that are clearly generated by a program. Fine for some things, sure. But there is a reason most of the diagrams that you remember the looks of were bespoke authored in a much more graphical environment.
Honestly I'd use it just for the auto-complete.
(Admittedly, I didn't look too hard for dedicated editing environments that could do it for DOT files specifically. I just wanted to make something real quick.)