refactor(golang): Use http provided constants for http methods (#3028)

* refactor(golang): Use http constants for methods

* regenerate samples

* fix: Only import strings when needed

* regenerate samples

* Only import fmt and strings when needed

* regenerate samples

Author: mcristina422

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java

@@ -361,10 +361,11 @@ public Map<String, Object> postProcessOperationsWithModels(Map<String, Object> o
                 iterator.remove();
         }
 
-        // this will only import "fmt" if there are items in pathParams
+        // this will only import "fmt" and "strings" if there are items in pathParams
         for (CodegenOperation operation : operations) {
             if (operation.pathParams != null && operation.pathParams.size() > 0) {
                 imports.add(createMapping("import", "fmt"));
+                imports.add(createMapping("import", "strings"));
                 break; //just need to import once
             }
         }

modules/openapi-generator/src/main/resources/go/api.mustache

@@ -7,7 +7,6 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
-	"strings"
 {{#imports}}	"{{import}}"
 {{/imports}}
 )
@@ -66,7 +65,7 @@ type {{{nickname}}}Opts struct {
 {{/hasOptionalParams}}
 func (a *{{{classname}}}Service) {{{nickname}}}(ctx context.Context{{#hasParams}}, {{/hasParams}}{{#allParams}}{{#required}}{{paramName}} {{{dataType}}}{{#hasMore}}, {{/hasMore}}{{/required}}{{/allParams}}{{#hasOptionalParams}}localVarOptionals *{{{nickname}}}Opts{{/hasOptionalParams}}) ({{#returnType}}{{{returnType}}}, {{/returnType}}*http.Response, error) {
 	var (
-		localVarHttpMethod   = strings.ToUpper("{{httpMethod}}")
+		localVarHttpMethod   = http.Method{{httpMethod}}
 		localVarPostBody     interface{}
 		localVarFormFileName string
 		localVarFileName     string

samples/client/petstore/go/go-petstore-withXml/.openapi-generator/VERSION

@@ -1 +1 @@
-4.0.0-SNAPSHOT
+4.0.1-SNAPSHOT

samples/client/petstore/go/go-petstore-withXml/README.md

@@ -12,14 +12,16 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 ## Installation
 
 Install the following dependencies:
-```
+
+```shell
 go get github.com/stretchr/testify/assert
 go get golang.org/x/oauth2
 go get golang.org/x/net/context
 go get github.com/antihax/optional
 ```
 
 Put the package under your project folder and add the following in import:
+
 ```golang
 import "./petstore"
 ```
@@ -70,18 +72,27 @@ Class | Method | HTTP request | Description
 
 ## Documentation For Models
 
+ - [AdditionalPropertiesAnyType](docs/AdditionalPropertiesAnyType.md)
+ - [AdditionalPropertiesArray](docs/AdditionalPropertiesArray.md)
+ - [AdditionalPropertiesBoolean](docs/AdditionalPropertiesBoolean.md)
  - [AdditionalPropertiesClass](docs/AdditionalPropertiesClass.md)
+ - [AdditionalPropertiesInteger](docs/AdditionalPropertiesInteger.md)
+ - [AdditionalPropertiesNumber](docs/AdditionalPropertiesNumber.md)
+ - [AdditionalPropertiesObject](docs/AdditionalPropertiesObject.md)
+ - [AdditionalPropertiesString](docs/AdditionalPropertiesString.md)
  - [Animal](docs/Animal.md)
  - [ApiResponse](docs/ApiResponse.md)
  - [ArrayOfArrayOfNumberOnly](docs/ArrayOfArrayOfNumberOnly.md)
  - [ArrayOfNumberOnly](docs/ArrayOfNumberOnly.md)
  - [ArrayTest](docs/ArrayTest.md)
  - [Capitalization](docs/Capitalization.md)
  - [Cat](docs/Cat.md)
+ - [CatAllOf](docs/CatAllOf.md)
  - [Category](docs/Category.md)
  - [ClassModel](docs/ClassModel.md)
  - [Client](docs/Client.md)
  - [Dog](docs/Dog.md)
+ - [DogAllOf](docs/DogAllOf.md)
  - [EnumArrays](docs/EnumArrays.md)
  - [EnumClass](docs/EnumClass.md)
  - [EnumTest](docs/EnumTest.md)
@@ -111,40 +122,56 @@ Class | Method | HTTP request | Description
 
 ## Documentation For Authorization
 
+
+
 ## api_key
-- **Type**: API key 
+
+- **Type**: API key
 
 Example
+
 ```golang
 auth := context.WithValue(context.Background(), sw.ContextAPIKey, sw.APIKey{
-	Key: "APIKEY",
-	Prefix: "Bearer", // Omit if not necessary.
+    Key: "APIKEY",
+    Prefix: "Bearer", // Omit if not necessary.
 })
 r, err := client.Service.Operation(auth, args)
 ```
+
+
 ## api_key_query
-- **Type**: API key 
+
+- **Type**: API key
 
 Example
+
 ```golang
 auth := context.WithValue(context.Background(), sw.ContextAPIKey, sw.APIKey{
-	Key: "APIKEY",
-	Prefix: "Bearer", // Omit if not necessary.
+    Key: "APIKEY",
+    Prefix: "Bearer", // Omit if not necessary.
 })
 r, err := client.Service.Operation(auth, args)
 ```
+
+
 ## http_basic_test
+
 - **Type**: HTTP basic authentication
 
 Example
+
 ```golang
 auth := context.WithValue(context.Background(), sw.ContextBasicAuth, sw.BasicAuth{
-	UserName: "username",
-	Password: "password",
+    UserName: "username",
+    Password: "password",
 })
 r, err := client.Service.Operation(auth, args)
 ```
+
+
 ## petstore_auth
+
+
 - **Type**: OAuth
 - **Flow**: implicit
 - **Authorization URL**: http://petstore.swagger.io/api/oauth/dialog
@@ -153,12 +180,14 @@ r, err := client.Service.Operation(auth, args)
  - **read:pets**: read your pets
 
 Example
+
 ```golang
 auth := context.WithValue(context.Background(), sw.ContextAccessToken, "ACCESSTOKENSTRING")
 r, err := client.Service.Operation(auth, args)
 ```
 
 Or via OAuth2 module to automatically refresh tokens and perform user authentication.
+
 ```golang
 import "golang.org/x/oauth2"
 
@@ -169,6 +198,7 @@ auth := context.WithValue(oauth2.NoContext, sw.ContextOAuth2, tokenSource)
 r, err := client.Service.Operation(auth, args)
 ```
 
+
 ## Author
 
 

samples/client/petstore/go/go-petstore-withXml/api/openapi.yaml

@@ -32,6 +32,9 @@ paths:
         description: Pet object that needs to be added to the store
         required: true
       responses:
+        200:
+          content: {}
+          description: successful operation
         405:
           content: {}
           description: Invalid input
@@ -56,6 +59,9 @@ paths:
         description: Pet object that needs to be added to the store
         required: true
       responses:
+        200:
+          content: {}
+          description: successful operation
         400:
           content: {}
           description: Invalid ID supplied
@@ -120,7 +126,8 @@ paths:
   /pet/findByTags:
     get:
       deprecated: true
-      description: Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
+      description: Multiple tags can be provided with comma separated strings. Use
+        tag1, tag2, tag3 for testing.
       operationId: findPetsByTags
       parameters:
       - description: Tags to filter by
@@ -173,6 +180,9 @@ paths:
           format: int64
           type: integer
       responses:
+        200:
+          content: {}
+          description: successful operation
         400:
           content: {}
           description: Invalid pet value
@@ -332,7 +342,8 @@ paths:
       x-codegen-request-body-name: body
   /store/order/{order_id}:
     delete:
-      description: For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors
+      description: For valid response try integer IDs with value < 1000. Anything
+        above 1000 or nonintegers will generate API errors
       operationId: deleteOrder
       parameters:
       - description: ID of the order that needs to be deleted
@@ -352,7 +363,8 @@ paths:
       tags:
       - store
     get:
-      description: For valid response try integer IDs with value <= 5 or > 10. Other values will generated exceptions
+      description: For valid response try integer IDs with value <= 5 or > 10. Other
+        values will generated exceptions
       operationId: getOrderById
       parameters:
       - description: ID of pet that needs to be fetched
@@ -1072,7 +1084,8 @@ paths:
       x-codegen-request-body-name: body
   /fake/body-with-file-schema:
     put:
-      description: For this test, the body for this request much reference a schema named `File`.
+      description: For this test, the body for this request much reference a schema
+        named `File`.
       operationId: testBodyWithFileSchema
       requestBody:
         content:
@@ -1350,17 +1363,11 @@ components:
     Dog:
       allOf:
       - $ref: '#/components/schemas/Animal'
-      - properties:
-          breed:
-            type: string
-        type: object
+      - $ref: '#/components/schemas/Dog_allOf'
     Cat:
       allOf:
       - $ref: '#/components/schemas/Animal'
-      - properties:
-          declawed:
-            type: boolean
-        type: object
+      - $ref: '#/components/schemas/Cat_allOf'
     Animal:
       discriminator:
         propertyName: className
@@ -2009,6 +2016,14 @@ components:
       xml:
         namespace: http://a.com/schema
         prefix: pre
+    Dog_allOf:
+      properties:
+        breed:
+          type: string
+    Cat_allOf:
+      properties:
+        declawed:
+          type: boolean
   securitySchemes:
     petstore_auth:
       flows:
@@ -2028,4 +2043,4 @@ components:
       type: apiKey
     http_basic_test:
       scheme: basic
-      type: http
+      type: http