f, err := os.Open(file)
	if err != nil {
		log.Fatal(err)
	}
	matches, hash, err := buildid.FindAndHash(f, id, 0)
	f.Close()
	if err != nil {
		log.Fatal(err)
	}

	// <= go 1.7 doesn't embed the contentID or actionID, so no slash is present
	if !strings.Contains(id, "/") {
		log.Fatalf("%s: build ID is a legacy format...binary too old for this tool", file)
	}