code: func ReadSecurityXattrToTarHeader(path string, hdr *tar.Header) error {
  	capability, _ := system.Lgetxattr(path, "security.capability")
  	if capability != nil {
  		hdr.Xattrs = make(map[string]string)
  		hdr.Xattrs["security.capability"] = string(capability)
  	}
  	return nil
  }
docs: // ReadSecurityXattrToTarHeader reads security.capability xattr from filesystem
  // to a tar header