There's a tradeoff space here, as that tweet indicates. Doing things generically makes the library less idiomatic, but means developers don't need to churn their library dependency as often. Go's a different language from Java, and it's less common to have to deal with casting, etc. As that tweet conversation indicates (particularly https://twitter.com/JimDanz/status/511732603884294145), we're also considering changing the Java library implementation in the future.
There's a tradeoff space here, as that tweet indicates. Doing things generically makes the library less idiomatic, but means developers don't need to churn their library dependency as often. Go's a different language from Java, and it's less common to have to deal with casting, etc. As that tweet conversation indicates (particularly https://twitter.com/JimDanz/status/511732603884294145), we're also considering changing the Java library implementation in the future.