My impression (and this was pre-Google and I haven't paid attention since I got here, so) is that it was Rob Pike's and Ken Thompson's project coming out of their long experience with Plan 9 and Inferno/Limbo. That it happened to meet some requirements for some Google projects -- I'm sure that might have been an intent. But that feels a bit like an explanation after the fact, since Go very obviously shows the biases and philosophy from the projects that the original authors had in their previous work.