[Go] Fix operation files clobbering model files. [2.4.0] (#7337)

* Prevent operation files clobbering model files.

* Update Tests

samples/server/petstore/go-api-server/go/model_user.go

@@ -0,0 +1,32 @@
+/*
+ * Swagger Petstore
+ *
+ * This is a sample server Petstore server.  You can find out more about Swagger at [http://swagger.io](http://swagger.io) or on [irc.freenode.net, #swagger](http://swagger.io/irc/).  For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * API version: 1.0.0
+ * Contact: apiteam@swagger.io
+ * Generated by: Swagger Codegen (https://github.com/swagger-api/swagger-codegen.git)
+ */
+
+package petstoreserver
+
+// A User who is purchasing from the pet store
+type User struct {
+
+	Id int64 `json:"id,omitempty"`
+
+	Username string `json:"username,omitempty"`
+
+	FirstName string `json:"firstName,omitempty"`
+
+	LastName string `json:"lastName,omitempty"`
+
+	Email string `json:"email,omitempty"`
+
+	Password string `json:"password,omitempty"`
+
+	Phone string `json:"phone,omitempty"`
+
+	// User Status
+	UserStatus int32 `json:"userStatus,omitempty"`
+}