UnhandledPromiseRejectionWarning：TypeError：createUser不是函数

如何解决UnhandledPromiseRejectionWarning：TypeError：createUser不是函数

我正在注册一个新用户。我收到错误 UnhandledPromiseRejectionWarning：TypeError：createuser不是函数

auth.js

const express = require("express");
const authrequests = express.Router();
const cors = require("cors");

var createuser = require("./export/authConstants");

// Register User
authrequests.post("/register",async (req,res) => {
  const userData = {
    firstname: req.body.firstname,lastname: req.body.lastname,email: req.body.email,phone: req.body.phone,password: req.body.password,created: new Date(),};
  await createuser(userData)
    .then((res) => {
      console.log(res)
      if (res.status == 200) {
        return res.status(200).json({ msg: 'Registered!' });
      } else if (res.status == 405) {
        return res.status(405).json({ error: 'User already exists' });
      } else {
        return res.status(400).json({ error: err });
      }
    })
    .catch(err => {
      return res.status(400).json({ error: err });
    })
});
module.exports = authrequests;

authConstants.js

const customers = require("./../../models/customers");

var hashPassword = require("./util/bcrypt");
var jwtCreate = require("./util/jwt");
var sendMail = require("./util/mail");
var BASE_URL = require("./../constants/constants");

//register
createuser = (userData) => {
    return new Promise(async (resolve,reject) => {
        customers.findOne({ where: { email: userData.email } })
            .then(async (user) => {
                if (!user) {
                    var hashResponse = await hashPassword(userData.password)
                    if (hashResponse.msg) {
                        userData.password = hashResponse.msg
                        customers.create(userData)
                            .then(async (user) => {
                                if (user) {
                                    var jwtResponse = await jwtCreate({ data: user.id,expiry: 172800 })
                                    if (jwtResponse.msg) {
                                        const url = `${BASE_URL}/auth/emailVerified/${jwtResponse.msg}`;
                                        var mailResponse = await sendMail({
                                            to: user.email,subject: 'Email Verification',html: `Click on the following link to verify your account: <a href="${url}">click here</a>`
                                        })
                                        if (mailResponse.msg) {
                                            resolve({ status: 200 })
                                        } else {
                                            reject({ error: mailResponse.err })
                                        }
                                    } else {
                                        reject({ error: jwtResponse.err })
                                    }
                                } else {
                                    reject({ error: "oops..! user creation Failed" })
                                }
                            })
                            .catch(err => {
                                reject({ error: err })
                            });

                    } else {
                        reject({ error: hashResponse.err })
                    }
                } else {
                    resolve({ status: 405 })
                }
            })
            .catch(err => {
                reject({ error: err })
            })
    })
};

bcrypt.js

const bcrypt = require("bcrypt");

//hashing password
hashPassword = async (password) => {
    await bcrypt.hash(password,10,(err,hash) => {
        if (hash) {
            return { msg: hash };
        } else {
            return { error: err };
        }
    })
};

jwt.js

const jwt = require("jsonwebtoken");

var EMAIL_SECRET = require("./../../constants/constants");

//jwt creation
jwtCreate = async (data) => {
    await jwt.sign(data.data,EMAIL_SECRET,{ expiresIn: data.expiry },token) => {
        if (token) {
            return { msg: token };
        } else {
            return { error: err };
        }
    })
};

mail.js

const nodemailer = require("nodemailer");

var MAIL_HOST = require("./../../constants/constants");
var EMAIL_USER = require("./../../constants/constants");
var EMAIL_PASS = require("./../../constants/constants");

//mail send
sendMail = async (data) => {
    let transporter = nodemailer.createTransport({
        host: MAIL_HOST,port: 587,secure: false,// true for 465,false for other ports
        auth: {
            user: EMAIL_USER,pass: EMAIL_PASS,},tls: {
            rejectUnauthorized: false,});
    await transporter.sendMail({
        from: EMAIL_USER,to: data.to,subject: data.subject,html: data.html
    },response) => {
        if (token) {
            return { msg: response };
        } else {
            return { error: err };
        }
    });
};

constants.js

const EMAIL_SECRET = "asdf1093KMnHGcvnkljvasdu09123nlasdasdf";
const MAIL_HOST = "mail.test.com";
const EMAIL_USER = "no_reply_auth@test.com";
const EMAIL_PASS = "JMkC+)*Lv";
const BASE_URL = "http://localhost:3001";

UnhandledPromiseRejectionWarning：TypeError：createuser不是函数 有什么我想念的吗..？还是整个流程都错了？？