Also, the project does indeed seem quite ambitious, maybe if you start with only an SGF parser you will be busy for a few weeks, and decide to switch languages based on your experience then
If you only want something to put into your CV, Java is still your best bet. Same goes if portability is an issue. The performance will not be an relevant with normal sized databases (<100k), or at least not due to language limitations.
Then again i mainly use C++ and it does have it's advantages, and for a go playing engine it would be my first choice.
If you do think you can stick with such a large project, i cannot recommend any scripting language such as Python, Ruby or Perl. These are the modern day Visual Basic in my opinion, good for small scale stuff and quick hacks, easy to learn and more lenient with some bad practices but unsuitable for any large application.