I'd be really delighted if you could show me a better tool for writing a parser, given a grammar in Golang than goyacc. You're absolutely right that the error reporting in yacc isn't that modern, but it's very functional, very powerful and (best of all), a lot of people have experience with it.

I certainly couldn't find any better tools in Golang when I started, but I wouldn't be surprised if someone had started one since.