I don't think adsense has done very well. Does Go generate revenue?

While Go doesn't directly generate any revenue, it's probably not without reason that Google is rewriting some important pieces (dl.google.com for example) in Go. I can imagine their engineers being much more expressive in Go than in C++, causing them to spend less time on writing the code as well as resulting in simpler code (easier to comprehend and maintain, so less time/money spent on maintenance). This doesn't generate revenue but it does optimize development processes, which could indirectly save them some money.