Version in “./docker-compose.yml“ is unsupported.

报错信息：

ERROR: Version in "./docker-compose.yml" is unsupported. You might be seeing this error because you're using the wrong Compose file version. Either specify a version of "2" (or "2.0") and place your service definitions under the `services` key, or omit the `version` key and place your service definitions at the root of the file to use version 1.
For more on the Compose file format versions, see https://docs.docker.com/compose/compose-file/

解决办法：

ubuntu版本过于旧了，需要在docker-compose.yml，修改verison值，之前是3.5，现改成2.0即可