Question: I was reading about Go, and I can see that it's very good and can be a language used by many developers in some months, but I want to decide a simple thing: **Learn Go or improve my Python or Ruby knowledge?**

Years developing with Python: 1  

Years developing with Ruby: 0.3

Answer: 
In reality, you should do both; if it's what you want. For me though, out of the two, I'd only look at Python. I have no real interest in languages that are so new.
First of all, it's a very very personal question, and my first recommendation will be , if you think so, try Go for one month or so, learning the basics, and then deciding... Each one has the mind fitted more to some particular languages than another...

I also would recommend keep using both Python and Ruby, if you're interested, you have enough experience to use them comfortably (I think), so the next months you could experience a great boost in your experience using them...

For an strict utilitarian point of view, learning Go extensively could be a risk move, but worthy if begins to being using and you're one of the very few people with some experience when everyone are just beginning to learn the syntax...