This is the resolver files

employee.resolvers.js

// Imported the employee model from the models directory
const models = require(`../models/index`);

const employeeResolvers = {
    Query: {
        /**
         * This method will return an array of employees according to the query
         */
        employees: (root, args, context, info) => {
            /**
             * This will find all the employees from the employees collection
             */
            return models.employee.find({})
        },
        /**
         * This method will find an employee details with respect to an ID.
         */
        employee: (root, { id }, context, info) => {
            return models.employee.findById(id)
        },
    },
    Mutation: {
        /**
         * This method will create an employee with parameters from the arguments
         */
        signUp: (root, args, context, info) => {
            return models.employee.create(args)
        },
        /**
         * this method will update an employee data with respect to an id
         */
        update: (root, { id, firstName, lastName, email, password }, context, info) => {
            let  updateInfo = {};
            return models.employee.findById(id).then((newEmployee) => {
                firstName ? newEmployee.firstName = firstName: "";
                lastName ? newEmployee.lastName = firstName: "";
                email ? newEmployee.email = email: "";
                password ? newEmployee.password = password: "";
                return newEmployee.save()
            })
        },
        /**
         * this method will delete an employee with respect to an ID
         */
        delete: (root, { id }, context, info) => {
            return models.employee.findByIdAndRemove(id)
        }
    }
}

module.exports = employeeResolvers;

index.js

// Imported both the resolvers for indexing
const messageResolvers = require(`./message.resolvers`);
const employeeResolvers = require(`./employee.resolvers`);
// Added all the resolvers into an array.
const resolvers =  [messageResolvers, employeeResolvers] ;
// exported resolvers as a object.
module.exports = { resolvers };

message.resolvers.js

const messageResolvers = {
    Query: {
        hello: () => 'Hello world'
    }
}

module.exports =  messageResolvers ;