const authenticationMiddleware = Intermediary.createMiddleware(
  (ctx, next, parent, queryArgs, gqlContext) => {
    if(!gqlContext.userId){
      throw new Error('NOT_ALLOWED');
    }
    return next(parent, queryArgs, gqlContext)
  }
)

const authenticator = new Intermediary([authenticationMiddleware]);

const loginResolver = (parent, queryArgs, gqlContext) => {
  // Unprotected resolver
}

const createProductResolver = authenticator.involve((parent, queryArgs, gqlContext) => {
  // Protected resolver
  // Only a logged in person can access
})