[Go] [Golang] [Client] No chance to obtain error payload

Description

No opportunity to get error payload without crutches
Error response models are generated, but not used
related to #9109

Swagger-codegen version

2.3.1

Swagger declaration file content or url

swagger: '2.0'
info:
  description: Example
  title: Example
  version: '1.0.0'
consumes:
  - application/json
produces:
  - application/json
paths:
  /rest:
    post:
      summary: "rest API"
      produces:
      - "application/json"
      responses:
        201:
          description: "tododo"
          schema:
            $ref: "#/definitions/foo"
        400:
          description: "dototo"
          schema:
            $ref: "#/definitions/bar"
definitions:
  foo:
    type: object
    properties:
      id:
        type: number
  bar:
    type: object
    properties:
      number:
        type: string

Generated code

look, it even doesn't use Bar model
moreover, in case of error localVarHttpResponse.Body is returned read and closed, so there isn't even an opportunity to get error payload by yourself, except parsing returned error, what is a disgusting crutch

func (a *DefaultApiService) RestPost(ctx context.Context) (Foo,  *http.Response, error) {
	var (
		localVarHttpMethod = strings.ToUpper("Post")
		localVarPostBody interface{}
		localVarFileName string
		localVarFileBytes []byte
	 	successPayload  Foo
	)

	// create path and map variables
	localVarPath := a.client.cfg.BasePath + "/rest"

	localVarHeaderParams := make(map[string]string)
	localVarQueryParams := url.Values{}
	localVarFormParams := url.Values{}


	// to determine the Content-Type header
	localVarHttpContentTypes := []string{ "application/json",  }

	// set Content-Type header
	localVarHttpContentType := selectHeaderContentType(localVarHttpContentTypes)
	if localVarHttpContentType != "" {
		localVarHeaderParams["Content-Type"] = localVarHttpContentType
	}

	// to determine the Accept header
	localVarHttpHeaderAccepts := []string{
		"application/json",
		}

	// set Accept header
	localVarHttpHeaderAccept := selectHeaderAccept(localVarHttpHeaderAccepts)
	if localVarHttpHeaderAccept != "" {
		localVarHeaderParams["Accept"] = localVarHttpHeaderAccept
	}
	r, err := a.client.prepareRequest(ctx, localVarPath, localVarHttpMethod, localVarPostBody, localVarHeaderParams, localVarQueryParams, localVarFormParams, localVarFileName, localVarFileBytes)
	if err != nil {
		return successPayload, nil, err
	}

	localVarHttpResponse, err := a.client.callAPI(r)
	if err != nil || localVarHttpResponse == nil {
		return successPayload, localVarHttpResponse, err
	}
	defer localVarHttpResponse.Body.Close()
	if localVarHttpResponse.StatusCode >= 300 {
		bodyBytes, _ := ioutil.ReadAll(localVarHttpResponse.Body)
		return successPayload, localVarHttpResponse, reportError("Status: %v, Body: %s", localVarHttpResponse.Status, bodyBytes)
	}

	if err = json.NewDecoder(localVarHttpResponse.Body).Decode(&successPayload); err != nil {
		return successPayload, localVarHttpResponse, err
	}


	return successPayload, localVarHttpResponse, err
}

Start with the generated DefaultApiService.RestPost entry point and the error-handling path around localVarHttpResponse.Body; review the related issue #9109 for context. Done should let callers obtain the declared 400 Bar error payload without relying on a formatted error string, with the response body handled safely.