I'm implementing Stripe for React Native and I'm trying to send the customerId to my Cloud Function using POST, but when I execute the code it returns in the console.log undefined

Cloud Function (Firebase)

exports.addCardForExistingCustomer = functions.https.onRequest(async (request, response) => {

   let id = await request.body.customer_id
  
   response.send({
     result: id
   })
});

Client side

const fetchPaymentSheetParams = async () => {
    const response = await fetch(`${API_URL}`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ customer_id: customerId })
    });
    const { result } = await response.json();

    console.log(result)

  };