[BUG] [GO] Issues when downloading files

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?

Description

one endpoint I have is for downloading files and so I defined the response as such in the contract:

      responses:
        '200':
          description: Resource returned OK.
          content:
            application/octet-stream:
              schema:
                type: string
                format: binary

in the now deprecated client, the endpoint definition was generated as such

/*
 * Execute executes the request
 * @return *os.File
 */
func (a *...ApiService) Get...Execute(r ApiGet...Request) (*os.File, *_nethttp.Response, GenericOpenAPIError) {
...

whereas, it is now generated as follows:

// Execute executes the request
//  @return *os.File
func (a *...ApiService) Get....Execute(r ApiGet...Request) (**os.File, *http.Response, error) {
	

I am not entirely sure why the returned type is **os.File instead of *os.File but this has the consequence to fail the download of files because the decode method does not handle this properly because that switch case https://github.com/OpenAPITools/openapi-generator/blob/0eca6291275394dab1bff79c9b4b6737202a9be9/modules/openapi-generator/src/main/resources/go/client.mustache#L423 is ignored since v is now of ***os.File

Start in modules/openapi-generator/src/main/resources/go/client.mustache around the referenced decode switch case. Reproduce the file-download endpoint with an application/octet-stream response and inspect the generated Go client’s Execute and decode behavior. Done means the generated return type is *os.File and the download is decoded successfully without the extra pointer level.