An experienced programmer friend of mine uses Go professionally. I was surprised to hear that he much prefers Java: he said that many concurrency libraries are available for Java and that Go's features are quite limited in comparison. He dislikes the fact that you have to break Go's poor type system to get many things (such as tests) to work. He has a pretty strong background in FP, so I think that perhaps Go's interfaces are the straw that broke the camel's back.

This made me realize that I'm still holding onto some biases about Java, and that it's worth a look. I did start to dabble in Scala (and I have experience with Clojure), but it seemed like I'd want to know some Java before doing Scala, whereas that didn't seem as necessary with Clojure.