Disclaimer: I use Java professionally on a daily basis and am learning Go in my free time.
I totally agree with all the points which most of you make. Firstly, you should almost never choose a language / technology which you want to learn when you are being given paid contract task to accomplish. It might be different at your full-time position, when picking new tool (after agreeing with the rest of the team or people making decisions) might really be a viable choice, giving you an edge in the end.
Beside that - if you're being paid by the hour, if you had been able to find a client who is willing to pay you for you to learn new stuff - stick to them as them as long as possible. Most of the clients with whom I had been dealing with would just fire me or terminate the contract.
As for the performance - and I'm not defending Go here - with discrepancies that big, I'd just assume that I don't know language and all of it's quirks and it's just me not using it properly. I know that you might had spent time profiling and optimising stuff, but sometimes the overall design of your program might be violating some of the rules of given language, punishing you with performance issues in the end.
(check http://www.techempower.com/benchmarks/ and the difference from first iteration to the last one, when people knowing each framework tested started pushing their favourite toys to give them an edge with misc optimisations)
From the two language which you had tested, Java was a way better choice here - no amount of hype around a language should win over mature libraries which were just suited for your job.
PS: and yes, I'd love to see generics in Go and can't understand any of the reasons for no.
I totally agree with all the points which most of you make. Firstly, you should almost never choose a language / technology which you want to learn when you are being given paid contract task to accomplish. It might be different at your full-time position, when picking new tool (after agreeing with the rest of the team or people making decisions) might really be a viable choice, giving you an edge in the end.
Beside that - if you're being paid by the hour, if you had been able to find a client who is willing to pay you for you to learn new stuff - stick to them as them as long as possible. Most of the clients with whom I had been dealing with would just fire me or terminate the contract.
As for the performance - and I'm not defending Go here - with discrepancies that big, I'd just assume that I don't know language and all of it's quirks and it's just me not using it properly. I know that you might had spent time profiling and optimising stuff, but sometimes the overall design of your program might be violating some of the rules of given language, punishing you with performance issues in the end.
(check http://www.techempower.com/benchmarks/ and the difference from first iteration to the last one, when people knowing each framework tested started pushing their favourite toys to give them an edge with misc optimisations)
From the two language which you had tested, Java was a way better choice here - no amount of hype around a language should win over mature libraries which were just suited for your job.
PS: and yes, I'd love to see generics in Go and can't understand any of the reasons for no.