code: func OpenFile(fileName string, flag int, perm os.FileMode) (*TzArchive, error) {
  	tz := new(TzArchive)
  	err := tz.Open(fileName, flag, perm)
  	return tz, err
  }
docs: // OpenFile is the generalized open call; most users will use Open
  // instead. It opens the named tar.gz file with specified flag
  // (O_RDONLY etc.) if applicable. If successful,
  // methods on the returned TzArchive can be used for I/O.
  // If there is an error, it will be of type *PathError.