GraphQL server showing circular relationship

server.js

const { ApolloServer, gql } = require("apollo-server");

const authors = [
  { id: 1, name: "J.K. Rowling" },
  { id: 2, name: "Michael Crichton" }
];

const books = [
  {
    authorId: 1,
    title: "Harry Potter and the Chamber of Secrets"
  },
  {
    authorId: 1,
    title: "Harry Potter and the Philosphers Stone"
  },
  {
    authorId: 2,
    title: "Jurassic Park"
  }
];

const schema = gql`
  type Query {
    getAuthor(id: Int): Author
  }

  type Book {
    title: String
    author: Author
  }

  type Author {
    name: String
    books: [Book]
  }
`;

const resolvers = {
  Query: {
    getAuthor(parent, args, context, info) {
      console.log("resolving getAuthor", parent, args);

      return authors.find(a => a.id === args.id);
    }
  },
  Author: {
    name(parent, args) {
      return parent.name;
    },
    books(parent, args) {
      return books.filter(book => book.authorId === parent.id);
    }
  },
  Book: {
    title(parent, args) {
      return parent.title;
    },
    author(parent, args) {
      return authors.find(author => author.id === parent.authorId);
    }
  }
};

// The ApolloServer constructor requires two parameters: your schema
// definition and your set of resolvers.
const server = new ApolloServer({ typeDefs: schema, resolvers, tracing: true });

// The `listen` method launches a web server.
server.listen().then(({ url }) => {
  console.log(`🚀  Server ready at ${url}`);
});

Sample query

  getAuthor(id: 1) {
    name
    books {
      title
      author {
        name
        books {
          title
          author {
            name
            books {
              title
            }
          }
        }
      }
    }
  }
}