code: func LookupGidFromFile(groupName, groupFile string) (gid int, err error) {
  	groups, err := parseGroupFile(groupFile)
  	if err != nil {
  		return -1, errwrap.Wrap(fmt.Errorf("error parsing %q file", groupFile), err)
  	}
  
  	group, ok := groups[groupName]
  	if !ok {
  		return -1, fmt.Errorf("%q group not found", groupName)
  	}
  
  	return group.Gid, nil
  }
docs: // LookupGid reads the group file specified by groupFile, and returns the gid of the group
  // specified by groupName.