[Error: Query.Mutation defined in resolvers, but not in schema]

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

const port = process.env.PORT || 4000;
const notes = [
    { id: '1', content: 'This is a note', author: 'Adam Scott' },
    { id: '2', content: 'This is another note', author: 'Harlow Everly' },
    { id: '3', content: 'Oh hey look, another note!', author: 'Riley Harrison' }
   ];

const typeDefs = gql `
    type Note {
        id: ID
        content: String
        author: String
    }

    type Query {
        hello: String
        notes: [Note]
        note(id: ID!): Note
    }

    type Mutation {
        newNote(content: String!): Note
    }
`;
const resolvers = {
    Query:{
        hello: () => 'Hello World',
        notes: () => notes,
        note: (parent, args) => {
            return notes.find(note => note.id == args.id);
        },
    Mutation: {
        newNote: (parent, args) => {
            let noteValue = {
                id : String(notes.length + 1),
                content : args.content,
                author: 'Adam Scott',
            };
            notes.push(noteValue);
            return noteValue;
        }
    }
    },
}

Some people had naming issues but seems that I’m using the same in resolver as well as in schema.
Please bare with me, this is my second day in GraphQL and Express. I removed intentionally imports and assignment of express object, middleware since it does not let me post.