This is purely a documentation issue.

As far as I can tell, looking at the README, wiki and compatibility table, the fact that the GopherJS compiler does not support cgo is not documented anywhere.

The compiler/build tool do try to detect when "C" is imported (i.e., when people try to use cgo) and do throw an error message:

• Better Error Message for Compiling Packages with CGO #215

• gopherjs/build/build.go

  Line 46 in 05b9d70

  CgoEnabled: true, // detect `import "C"` to throw proper error

• Implement runtime.NumCgoCall() #386 (comment)

That's good, but doesn't replace the need to actually document the fact.

I've noticed this issue after seeing the question come up here, and I couldn't find any documentation to refer people to.