mailgun.messages is not a function - node.js

Question

I am trying to get my e-commerce web app to send emails on purchasing but when I try to pay for things I get the mailgun.messages is not a function I've reverted changes and re coded it twice but this is a different error I'm not sure how to resolve this. Is there another way to use mailgun's api? Here is the code below:
orderRoutes.js:
orderRouter.put(
"/:id/pay",
isAuth,
expressAsyncHandler(async (req, res) => {
const order = await Order.findById(req.params.id).populate(
"user",
"email firstName"
);
if (order) {
order.isPaid = true;
order.paidAt = Date.now();
order.paymentResult = {
id: req.body.id,
status: req.body.status,
update_time: req.body.update_time,
email_address: req.body.email_address,
};
const updateOrder = await order.save();
mailgun.messages().send(
{
from: "Sales <sales#cocoTiCosmetics.com>",
to: `${order.user.firstName} <${order.user.email}>`,
subject: `New Order ${order._id}`,
html: payOrderEmailTemplate(order),
},
(error, body) => {
if (error) {
console.log(error);
} else {
console.log(body);
}
}
);
res.send({ message: "Order Paid", order: updateOrder });
} else {
res.status(404).send({ message: "Order Not Found" });
}
})
);
utils.js
export const mailgun = () =>
mg({
apiKey: process.env.MAILGUN_API_KEY,
domain: process.env.MAILGUN_DOMAIN,
});