go/src/cmd/go/internal/toolchain/path_unix.go

// pathDirs returns the directories in the system search path.
func pathDirs() []string { … }

// pathVersion returns the Go version implemented by the file
// described by de and info in directory dir.
// The analysis only uses the name itself; it does not run the program.
func pathVersion(dir string, de fs.DirEntry, info fs.FileInfo) (string, bool) { … }