code: func HelperProgramCredentialsSource(executable string, args ...string) CredentialsSource {
  	if !filepath.IsAbs(executable) {
  		panic("NewCredentialsSourceHelperProgram requires absolute path to executable")
  	}
  
  	fullArgs := make([]string, len(args)+1)
  	fullArgs[0] = executable
  	copy(fullArgs[1:], args)
  
  	return &helperProgramCredentialsSource{
  		executable: executable,
  		args:       fullArgs,
  	}
  }
docs: // HelperProgramCredentialsSource returns a CredentialsSource that runs the
  // given program with the given arguments in order to obtain credentials.
  //
  // The given executable path must be an absolute path; it is the caller's
  // responsibility to validate and process a relative path or other input
  // provided by an end-user. If the given path is not absolute, this
  // function will panic.
  //
  // When credentials are requested, the program will be run in a child process
  // with the given arguments along with two additional arguments added to the
  // end of the list: the literal string "get", followed by the requested
  // hostname in ASCII compatibility form (punycode form).