<!--
Please follow the issue template below for bug reports and feature requests.
Also please indicate in the issue title which language/library is concerned. Eg:  [JAVA] Bug generating foo with bar 
-->

##### Description

<!-- describe what is the question, suggestion or issue and why this is a problem for you. -->

##### openapi-generator version

<!-- which version of openapi-generator are you using, is it a regression? -->

##### OpenAPI declaration file content or url

<!-- if it is a bug, a json or yaml that produces it.
If you post the code inline, please wrap it with
```yaml
(here your code)
```
(for YAML code) or
```json
(here your code)
```
(for JSON code), so it becomes more readable. If it is longer than about ten lines,
please create a Gist (https://gist.github.com) or upload it somewhere else and
link it here.
  -->

##### Command line used for generation

<!-- including the language, libraries and various options -->

##### Steps to reproduce

<!-- unambiguous set of steps to reproduce the bug.-->

##### Related issues/PRs

<!-- has a similar issue/PR been reported/opened before? Please do a search in https://github.com/openapi-json-schema-tools/openapi-json-schema-generator/issues?utf8=%E2%9C%93&q=is%3Aissue%20 -->

##### Suggest a fix/enhancement

<!-- if you can't fix the bug yourself, perhaps you can point to what might be
  causing the problem (line of code or commit), or simply make a suggestion -->

