spring boot starter graphql not working

I had the same issue using Spring boot 2.0.0 (M6). Switching back to 1.5.8.RELEASE solved the problem. They're working on the issue, it will be released as soon as there is a non milestone release for Spring boot 2.x

https://github.com/graphql-java/graphql-spring-boot/issues/40

https://github.com/graphql-java/graphql-spring-boot/pull/36