The provided definition does not specify a valid version field.
Please indicate a valid Swagger or OpenAPI version field. Supported version fields are swagger: "2.0" and those that match openapi: 3.0.n (for example, openapi: 3.0.0).
可能的原因:
api中的Controller/Action 请加入[HttpPost]或者 [HTTPGet]
swagger Unable to render this definition
原文：https://www.cnblogs.com/lonelyxmas/p/11525988.html