It's used pretty extensively. Standard language for log analysis (across all products), plus a bunch of newer microservices are written in it. It tends to be more internal tools & services, because...
Google has the disadvantage of history: a lot of the primary products were written before Go came out, and a lot of the newer products are spin-outs from existing codebases. It's very difficult to switch the language of a large existing codebase, and particularly difficult to switch the language to Go (because its runtime is incompatible with C++ and the JVM). You pretty much need a clean-sheet project, which occurs when there's a new microservice that talks via RPC, but almost never occurs in a primary consumer-facing product.
