The Sling GraphQL Core module allows for running GraphQL queries in Sling, using dynamically built GraphQL schemas and OSGi services for data fetchers (aka "resolvers") which provide the data.
See the o.a.s.graphql.core Git repository for more information.
The GraphQL Sample Website module provides a complete sample which uses GraphQL queries (and Handlebars templates) on both the server and client sides, to demonstrate the various modes that the GraphQL Core module supports.
Other Sling GraphQL modules can be listed with this GitHub repository query.