Swift is not properly supported on linux, which is Google's main platforms.
Google has been gradually moving away from C++ and Java since 2012. See this quora post with multiple references from Google employees.
https://www.quora.com/How-is-Go-used-at-Google-What-could-be...
Go is mostly a Docker/Kubernetes thing.
You will even notice that it is seldom supported when they announce new server products SDKs.