I wonder if what I heard from some people is true, that at Google Go isn't used as widely as people think.
The fact that it was developed at Google is incidental. That's where Robert Griesemer (Oberon) and Rob Pike (Plan 9) and Ken Thompson (Unix, Plan 9) and Russ Cox (Plan 9) and Ian Lance Taylor, etc., happened to be employed.
So where ever else Go is used it is decent enough.
A lot of legacy code is C++ or Java, but almost all of the new software being developed uses Go.