code: func saveTenantID(path string, tenantID string) error {
  	var perm os.FileMode = 0600
  
  	dir := filepath.Dir(path)
  	if err := os.MkdirAll(dir, os.ModePerm); err != nil {
  		return fmt.Errorf("Failed to create directory %s: %v", dir, err)
  	}
  
  	f, err := ioutil.TempFile(dir, "tenantid")
  	if err != nil {
  		return fmt.Errorf("Failed to create temp file: %v", err)
  	}
  	defer f.Close()
  
  	fp := f.Name()
  	if _, err := f.Write([]byte(tenantID)); err != nil {
  		return fmt.Errorf("Failed to write tenant ID to file: %v", err)
  	}
  	f.Close()
  
  	// atomic move by rename
  	if err := os.Rename(fp, path); err != nil {
  		return fmt.Errorf("Failed to rename file. src=%s dst=%s error=%v", fp, path, err)
  	}
  	if err := os.Chmod(path, perm); err != nil {
  		return fmt.Errorf("Failed to chmod the file %s: %v", path, err)
  	}
  	return nil
  }
docs: // saveTenantID performs an atomic write to the path with given tenantID contents.