Use golang's provided method names (gin) (#2983)

* Use golang's provided method names (gin)

This commit modifies the gin template for the router to leverage the http constants for method types as defined by RFC 7231 section 4.3. These are documented on:

https://golang.org/pkg/net/http/#pkg-constants

This removes the need for the `strings` dependency and does not require any new dependencies, as `net/http` is already imported.

* Remove strings dependency which is no longer used

* Update samples

modules/openapi-generator/src/main/resources/go-gin-server/routers.mustache

@@ -3,7 +3,6 @@ package {{packageName}}
 
 import (
 	"net/http"
-	"strings"
 
 	"github.com/gin-gonic/gin"
 )
@@ -28,13 +27,13 @@ func NewRouter() *gin.Engine {
 	router := gin.Default()
 	for _, route := range routes {
 		switch route.Method {
-		case "GET":
+		case http.MethodGet:
 			router.GET(route.Pattern, route.HandlerFunc)
-		case "POST":
+		case http.MethodPost:
 			router.POST(route.Pattern, route.HandlerFunc)
-		case "PUT":
+		case http.MethodPut:
 			router.PUT(route.Pattern, route.HandlerFunc)
-		case "DELETE":
+		case http.MethodDelete:
 			router.DELETE(route.Pattern, route.HandlerFunc)
 		}
 	}
@@ -50,14 +49,14 @@ func Index(c *gin.Context) {
 var routes = Routes{
 	{
 		"Index",
-		"GET",
+		http.MethodGet,
 		"{{{basePathWithoutHost}}}/",
 		Index,
 	},{{#apiInfo}}{{#apis}}{{#operations}}{{#operation}}
 
 	{
 		"{{operationId}}",
-		strings.ToUpper("{{httpMethod}}"),
+		http.Method{{httpMethod}},
 		"{{{basePathWithoutHost}}}{{{path}}}",
 		{{operationId}},
 	},{{/operation}}{{/operations}}{{/apis}}{{/apiInfo}}

samples/server/petstore/go-gin-api-server/go/routers.go

@@ -11,7 +11,6 @@ package petstoreserver
 
 import (
 	"net/http"
-	"strings"
 
 	"github.com/gin-gonic/gin"
 )
@@ -36,13 +35,13 @@ func NewRouter() *gin.Engine {
 	router := gin.Default()
 	for _, route := range routes {
 		switch route.Method {
-		case "GET":
+		case http.MethodGet:
 			router.GET(route.Pattern, route.HandlerFunc)
-		case "POST":
+		case http.MethodPost:
 			router.POST(route.Pattern, route.HandlerFunc)
-		case "PUT":
+		case http.MethodPut:
 			router.PUT(route.Pattern, route.HandlerFunc)
-		case "DELETE":
+		case http.MethodDelete:
 			router.DELETE(route.Pattern, route.HandlerFunc)
 		}
 	}
@@ -58,147 +57,147 @@ func Index(c *gin.Context) {
 var routes = Routes{
 	{
 		"Index",
-		"GET",
+		http.MethodGet,
 		"/v2/",
 		Index,
 	},
 
 	{
 		"AddPet",
-		strings.ToUpper("Post"),
+		http.MethodPost,
 		"/v2/pet",
 		AddPet,
 	},
 
 	{
 		"DeletePet",
-		strings.ToUpper("Delete"),
+		http.MethodDelete,
 		"/v2/pet/:petId",
 		DeletePet,
 	},
 
 	{
 		"FindPetsByStatus",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/pet/findByStatus",
 		FindPetsByStatus,
 	},
 
 	{
 		"FindPetsByTags",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/pet/findByTags",
 		FindPetsByTags,
 	},
 
 	{
 		"GetPetById",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/pet/:petId",
 		GetPetById,
 	},
 
 	{
 		"UpdatePet",
-		strings.ToUpper("Put"),
+		http.MethodPut,
 		"/v2/pet",
 		UpdatePet,
 	},
 
 	{
 		"UpdatePetWithForm",
-		strings.ToUpper("Post"),
+		http.MethodPost,
 		"/v2/pet/:petId",
 		UpdatePetWithForm,
 	},
 
 	{
 		"UploadFile",
-		strings.ToUpper("Post"),
+		http.MethodPost,
 		"/v2/pet/:petId/uploadImage",
 		UploadFile,
 	},
 
 	{
 		"DeleteOrder",
-		strings.ToUpper("Delete"),
+		http.MethodDelete,
 		"/v2/store/order/:orderId",
 		DeleteOrder,
 	},
 
 	{
 		"GetInventory",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/store/inventory",
 		GetInventory,
 	},
 
 	{
 		"GetOrderById",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/store/order/:orderId",
 		GetOrderById,
 	},
 
 	{
 		"PlaceOrder",
-		strings.ToUpper("Post"),
+		http.MethodPost,
 		"/v2/store/order",
 		PlaceOrder,
 	},
 
 	{
 		"CreateUser",
-		strings.ToUpper("Post"),
+		http.MethodPost,
 		"/v2/user",
 		CreateUser,
 	},
 
 	{
 		"CreateUsersWithArrayInput",
-		strings.ToUpper("Post"),
+		http.MethodPost,
 		"/v2/user/createWithArray",
 		CreateUsersWithArrayInput,
 	},
 
 	{
 		"CreateUsersWithListInput",
-		strings.ToUpper("Post"),
+		http.MethodPost,
 		"/v2/user/createWithList",
 		CreateUsersWithListInput,
 	},
 
 	{
 		"DeleteUser",
-		strings.ToUpper("Delete"),
+		http.MethodDelete,
 		"/v2/user/:username",
 		DeleteUser,
 	},
 
 	{
 		"GetUserByName",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/user/:username",
 		GetUserByName,
 	},
 
 	{
 		"LoginUser",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/user/login",
 		LoginUser,
 	},
 
 	{
 		"LogoutUser",
-		strings.ToUpper("Get"),
+		http.MethodGet,
 		"/v2/user/logout",
 		LogoutUser,
 	},
 
 	{
 		"UpdateUser",
-		strings.ToUpper("Put"),
+		http.MethodPut,
 		"/v2/user/:username",
 		UpdateUser,
 	},