code: func FindCgroupMountpoint(subsystem string) (string, error) {
  	f, err := os.Open("/proc/self/mountinfo")
  	if err != nil {
  		return "", err
  	}
  	scanner := bufio.NewScanner(f)
  	for scanner.Scan() {
  		txt := scanner.Text()
  		fields := strings.Split(txt, " ")
  		for _, opt := range strings.Split(fields[len(fields)-1], ",") {
  			if opt == subsystem {
  				return fields[4], nil
  			}
  		}
  	}
  	if err := scanner.Err(); err != nil {
  		return "", err
  	}
  
  	return "", NewNotFoundError(subsystem)
  }
docs: // https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt