const runtime/internal/sys.GOOS

2 uses

	runtime/internal/sys (current package)
		zgoos_darwin.go#L8: const GOOS = `darwin`

	runtime
		extern.go#L253: const GOOS string = sys.GOOS

The pages are generated with Golds v0.2.8-preview. (GOOS=darwin GOARCH=arm64)