Hi, I'm the developer for GoLucene. For your question, I don't think there would be huge performance gain from a Go version but it depends. As you can see, Lucene Java is already optimized to teeth. FAQ for Lucy also indicates, that different platforms has different focus. For Go's version, its benefits can be:
1) quick start speed; (used as a standalone index tool?)
2) able to be embedded in Go app; (my major interest here for cloud app deploy)
3) goroutine which I think can be faster in certain case;
4) ready-to-use byte, array utilities which I think can reduce the code size, and lead to easy maintenance.
Though it started as a pet project, I'm pretty serious about this.
Thanks for your interest,
Ian