How to use middleware [Directives] in GraphQL resolvers?

Question

I've been using github.com/graphql-go/graphql library for my GraphQL project. Currently, I'm trying to add authorization middleware to the following query.

Using github.com/99designs/gqlgen library we can achieve this by adding Directives. But couldn't find a proper example to do so using github.com/graphql-go/graphql.

query := graphql.NewObject(graphql.ObjectConfig{
    Name: "RootQuery",
    Fields: graphql.Fields{
        "user": &graphql.Field{
            Type:        userType,
            Description: "Get a user by ID.",
            Args: graphql.FieldConfigArgument{
                "id":   &graphql.ArgumentConfig{Type: graphql.ID},
            },
            Resolve: func(p graphql.ResolveParams) (interface{}, error) {
                    ...
                    return user
            },
        },
    },
})

Can anyone please suggest how I can add Authorization middleware to this resolver ?