'Folklore\GraphQL\ServiceProvider',

'GraphQL' => 'Folklore\GraphQL\Support\Facades\GraphQL',

$app->register(Folklore\GraphQL\LumenServiceProvider::class);

$app->withFacades();

class_alias(\Folklore\GraphQL\Support\Facades\GraphQL::class, 'GraphQL');

$app->configure('graphql');
...
$app->register(Folklore\GraphQL\LumenServiceProvider::class)

class UserType extends BaseType
{
    //...
    protected function fields()
    {
        return [
            'id' => [
                'type' => Type::id(),
                'description' => 'The user id'
            ],
            'email' => [
                'type' => Type::string(),
                'description' => 'The user email'
            ]
        ]
    }
    //...
}

<?php
return [
    //...
    'types' => [
        \App\GraphQL\Type\UserType::class
    ]
    //...
];

class AppServiceProvider extends ServiceProvider
{
    //...
    public function boot()
    {
        GraphQL::addType(\App\GraphQL\Type\UserType::class);
    }
    //...  
}

class UserType extends BaseType
{
    //...
    protected function args()
    {
        return [
            'id' => [
                'name' => 'id',
                'type' => Type::nonNull(Type::id()),
                'description' => 'The user id'
            ]
        ]
    }
    protected function type()
    {
        //This is the type we've created the step before
        return GraphQL::type('User');
    }
    public function resolve($root, $args, $context, ResolveInfo $info)
    {
        //Take the arguments and get a user from an eloquent model
        $user = User::find($args['id']);
        return $user
    }
}

<?php
return [
    //...
    'schemas' => [
        'default' => [
            'query' => [
                'user' => \App\GraphQL\Query\UserQuery::class
            ]
            //...
        ]
    ]
    //...
];

class AppServiceProvider extends ServiceProvider
{
    //...
    public function boot()
    {
        GraphQL::addSchema('default', [
            'query' => [
                'user' => \App\GraphQL\Query\UserQuery::class
            ]
        ]);
    }
    //...  
}