code: func combineEndpointErrors(allErrors map[string]error) error {
  	var parts []string
  	for ep, err := range allErrors {
  		parts = append(parts, fmt.Sprintf("%s: %s", ep, err))
  	}
  	return errors.New(strings.Join(parts, ", "))
  }
docs: // combineEndpointErrors takes a mapping of Docker API endpoints to errors encountered
  // while talking to them and returns a single error that contains all endpoint URLs
  // along with error for each URL.