Node-Fetch Mapping Error - Cannot read property 'map' of undefined"

Getting an error with the "map" part when I try and run it Cannot read property 'map' of undefined"

The customers const is declared above so not sure. Where is the undefined is coming from? Does the map need declaring?

const AWS = require('aws-sdk'),
  ses = new AWS.SES(),
  fetch = require('node-fetch');

exports.handler = async (event) => {
  console.log(event.customer_id);

  const customers = await getCustomers();

  customers.map(async customer => await sendEmailToCustomer(customer));

  const customersEmailsPromises = customers.map(async customer => await sendEmailToCustomer(customer));

}

async function getCustomers() {
  try {
    const resp = await fetch('https://3objects.netlify.com/3objects.json');
    const json = await resp.json();

    return json;
  }
  catch(e) {
    throw e;
  }
}

const sendEmailToCustomer = (customer) => new Promise((resolve, reject) => {
  ses.sendEmail({
    Destination:
      { ToAddresses: [customer.email] },
    Message:
      {
        Body: { Text: { Data: `Your contact option is ${customer.customer_id}` } },
        Subject: { Data: "Your Contact Preference" }
      },
    Source: "sales@example.com"
  }, (error, result => {
    if (error) return reject(error);
    resolve(result);
    console.log(result);
  })
  );
})

from Node-Fetch Mapping Error - Cannot read property 'map' of undefined"