graphql-wp
A GraphQL endpoint for WordPress that's easy to customize.
This is a WordPress Plugin that exposes a GraphQL endpoint at /graphql.
Uses this excellent graphql-php library.
Supports Relay Connections.
Install
composer require mohiohio/graphql-wp
If your aren't familiar with using composer with WordPress I'd recommend using a setup like bedrock. Otherwise you will at the least need to require autoload.php for this to work.
Using
The best way to explore / develop with this is by visiting /graphiql after installation. This will show you the endpoints and arguments that are available. Note this will only work if you are a logged in admin user.

wp_query
This is designed to follow WordPress' existing WP Query functions. So as a rule you can pass the same parameters as your can to WP Query*.
*In reality there are a lot of params you can pass to WP_Query, and I've only implemented the ones that I've needed so far. But adding more is trivial as the arguments are just passed directly to the get_posts function, so its just a matter of defining them in the schema.
query example {