added to petstore an example to trigger the issue which this PR fixes

modules/openapi-generator/src/test/resources/3_0/go-server/petstore.yaml

@@ -582,6 +582,24 @@ paths:
               $ref: '#/components/schemas/User'
         description: Created user object
         required: true
+    put:
+      tags:
+        - user
+      summary: Create user
+      description: This can only be done by the logged in user.
+      operationId: createUserNullable
+      responses:
+        default:
+          description: successful operation
+      security:
+        - api_key: []
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/UserNullable'
+        description: Created user object, with a nullable bodyParam
+        required: true
   /user/createWithArray:
     post:
       tags:
@@ -1052,6 +1070,66 @@ components:
         name: User
       required:
         - deepSliceModel
+    UserNullable:
+      title: a User
+      description: A User who is purchasing from the pet store
+      type: object
+      nullable: true
+      properties:
+        id:
+          type: integer
+          format: int64
+        username:
+          type: string
+        firstName:
+          type: string
+        lastName:
+          type: string
+        email:
+          type: string
+        password:
+          type: string
+        phone:
+          type: string
+          nullable: true
+        userStatus:
+          type: integer
+          format: int32
+          description: User Status
+        deepSliceModel:
+          nullable: true
+          type: array
+          description: An array 1-deep.
+          items:
+            type: array
+            description: An array 2-deep.
+            items:
+              type: array
+              description: An array 3-deep.
+              items:
+                $ref: '#/components/schemas/Tag'
+        deepSliceMap:
+          type: array
+          description: An array 1-deep.
+          items:
+            type: array
+            description: An array 2-deep.
+            items:
+              title: an Object
+              type: object
+              description: An array 3-deep.
+              properties:
+                tag:
+                  $ref: '#/components/schemas/Tag'
+                Pet:
+                  type: array
+                  description: An array of pet.
+                  items:
+                    $ref: '#/components/schemas/Pet'
+      xml:
+        name: User
+      required:
+        - deepSliceModel
     Tag:
       title: Pet Tag
       description: A tag for a pet

samples/server/petstore/go-api-server/.openapi-generator/FILES

@@ -27,5 +27,6 @@ go/model_special_info.go
 go/model_species.go
 go/model_tag.go
 go/model_user.go
+go/model_user_nullable.go
 go/routers.go
 main.go

samples/server/petstore/go-api-server/api/openapi.yaml

@@ -605,6 +605,24 @@ paths:
       summary: Create user
       tags:
       - user
+    put:
+      description: This can only be done by the logged in user.
+      operationId: createUserNullable
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/UserNullable'
+        description: "Created user object, with a nullable bodyParam"
+        required: true
+      responses:
+        default:
+          description: successful operation
+      security:
+      - api_key: []
+      summary: Create user
+      tags:
+      - user
   /user/createWithArray:
     post:
       description: ""
@@ -1240,6 +1258,211 @@ components:
       type: object
       xml:
         name: User
+    UserNullable:
+      description: A User who is purchasing from the pet store
+      example:
+        firstName: firstName
+        lastName: lastName
+        password: password
+        userStatus: 6
+        phone: phone
+        deepSliceModel:
+        - - - name: name
+              id: 1
+            - name: name
+              id: 1
+          - - name: name
+              id: 1
+            - name: name
+              id: 1
+        - - - name: name
+              id: 1
+            - name: name
+              id: 1
+          - - name: name
+              id: 1
+            - name: name
+              id: 1
+        id: 0
+        deepSliceMap:
+        - - tag:
+              name: name
+              id: 1
+            Pet:
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+          - tag:
+              name: name
+              id: 1
+            Pet:
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+        - - tag:
+              name: name
+              id: 1
+            Pet:
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+          - tag:
+              name: name
+              id: 1
+            Pet:
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+            - photoUrls:
+              - photoUrls
+              - photoUrls
+              name: doggie
+              id: 0
+              category:
+                name: name
+                id: 6
+              tags:
+              - name: name
+                id: 1
+              - name: name
+                id: 1
+              status: available
+        email: email
+        username: username
+      nullable: true
+      properties:
+        id:
+          format: int64
+          type: integer
+        username:
+          type: string
+        firstName:
+          type: string
+        lastName:
+          type: string
+        email:
+          type: string
+        password:
+          type: string
+        phone:
+          nullable: true
+          type: string
+        userStatus:
+          description: User Status
+          format: int32
+          type: integer
+        deepSliceModel:
+          description: An array 1-deep.
+          items:
+            description: An array 2-deep.
+            items:
+              description: An array 3-deep.
+              items:
+                $ref: '#/components/schemas/Tag'
+              type: array
+            type: array
+          nullable: true
+          type: array
+        deepSliceMap:
+          description: An array 1-deep.
+          items:
+            description: An array 2-deep.
+            items:
+              $ref: '#/components/schemas/an_Object'
+            type: array
+          type: array
+      required:
+      - deepSliceModel
+      title: a User
+      type: object
+      xml:
+        name: User
     Tag:
       description: A tag for a pet
       example: