[BUG][go] When oneOf is present in the object object properties are ignored.

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

When oneOf is present on the object the other properities aren't included in that object.

openapi-generator version

6.2.1

OpenAPI declaration file content or url

    RegionConfig:
      type: object
      discriminator:
        mapping:
          AWS: '#/components/schemas/AWSRegionConfigView'
          AZURE: '#/components/schemas/AzureRegionConfigView'
        propertyName: providerName
      oneOf:
      - $ref: '#/components/schemas/RegionConfigView'
      properties:
        test:
          type: integer
          format: int32

test property would not be included into object.

Steps to reproduce

Related issues/PRs

Suggest a fix

Start with the provided OpenAPI declaration and reproduce generation for the Go target using version 6.2.1 or the latest available version. Inspect the generated object for RegionConfig and compare whether the test property is retained alongside oneOf. Done means the generated object includes the declared properties as well as the oneOf-related structure.