tests/core/go_binary/broken_cgo.go - third_party/github.com/bazelbuild/rules_go - Git at Google

 // +build cgo

 // This file will not compile and its inclusion in a build is used to ensure
 // that a binary was built in pure mode.
 package main

 import "non/existent/pkg"
	// +build cgo

	// This file will not compile and its inclusion in a build is used to ensure
	// that a binary was built in pure mode.
	package main

	import "non/existent/pkg"