I have used many schematic editors and they all handle different font sizes correctly, even letting you choose different fonts and styles within the same document. It is not difficult to figure out how much space a piece of text takes up, and scale the other elements to fit.

If the actual connectivity of the parts in your schematic changes with font size, then I will quite frankly say "you're doing it wrong".

If Go maintainers decide to change the font metrics you will have the same problem. Distributing your own font (as you have mentioned) is the right way to go.

for the end-user? nope, because this application doesn't look like the rest of their applications, and ignores their preferences.

for the developer? yes, because their application will look the same regardless of platform it's deployed on.

But as we've learned with Responsive Design, having a single "my way" of presenting an interface regardless of end-user preferences and device capabilities is a Bad Thing. Interfaces need to be configurable by the user not fixed by the designer.

I like the font, though. Makes my code look sexy, and that's hard to do ;)