Even though the languages may seem quite similar, the cultures of the two communities and how software tends to be written in each language is vastly different in my experience.
In my opinion, Java is a great language that has was ruined by enterprise adoption. SOAP, JavaBeans etc, set this precedent of crazy over-engineered solutions in Java and it has never really recovered.
Go seems to attract C and Python programmers that prefer simpler interfaces and doing more with less. It is just a different culture, though I would agree from a language perspective they are very similar.
Which is great, choices are good and you can pick the culture you prefer, but you can only say the languages are similar if you ignore this huge chasm in their cultures.
