right click searches don't handle go mod paths

[rjkroege]

When using go modules, one might end up with a path like this:

/Users/rjkroege/tools/gopkg/pkg/mod/github.com/fhs/mux9p@v0.2.0/mux9p.go:184

for fhs's mux package used by Edwood. But right clicking on these doesn't seem to treat them as paths. Presumably one of Edwood or plumb is sad about the @ in the path.