[golang] additionalProperties produces empty struct

Created by: etherealjoy

Description

additionalProperties for object produces empty fields

openapi-generator version

master 3.1.x

OpenAPI declaration file content or url

swagger: "2.0"
info:
  description: app
  version: 1.0.0
  title: Application
  
host: localhost:32000
basePath: /api/v1.0
schemes:
- http

tags:
- name: ApplicationResources
  x-displayName: "ApplicationResources"
  description: |
    "Resources managed by the application instance."
    
paths:
  /default/ApiTestSetup: 
    get:
      description: "Test Setup"
      operationId: apiTestConfigurationGet
      responses:
        200:
          description: "Successful response"
          schema: 
            $ref: "#/definitions/TestEndPointConfig"          
        400:
          description: "The request was not successfully executed."           
  
definitions:
      
  TestEndPointConfig : 
    type : "object"
    additionalProperties :
      type: "string"

Code Produced

type TestEndPointConfig struct {
} 

Command line used for generation

java -jar /home/dev/openapi-generator/modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -i ./app.yaml -o ./gengo-server -l go-server --additional-properties packageName=app --additional-properties hideGenerationTimestamp=true

Suggest a fix/enhancement