gswagger/testdata/extension.json

{
  "info": {
    "title": "test openapi title",
    "version": "test openapi version"
  },
  "openapi": "3.0.0",
  "paths": {
    "/users": {
      "get": {
        "responses": {
          "default": {
            "description": ""
          }
        },
        "x-extension-field": {
          "foo": "bar"
        }
      }
    }
  }
}