Node.js 如何在nodejs服务器代码中使用Mailgun以html格式向mail发送文件？

我正在收集信息，并通过HTML表单附加文件，并在邮枪的帮助下将其发送到邮件。我想通过表单手动附加文件。附加到表单的文件已发送到邮件。我被困在这个问题上了。有人能帮我吗

这是我的html文件

 <div class="form-group">
                            <label for="district"> District</label>
                            <select id="output" onchange="random_function1()" class="form-control"  placeholder="Your District..." >
                            </select>
                        </div>


                        <div class="form-group">
                            <label for="messege"> Subject of Correspondence</label>
                            <input type="text" class="form-control" id="messege" name="messege" placeholder="Your suject of contact..." required maxlength="150">
                        </div>


                        <div class="form-group">
                            <label for="attachments"> Document Upload:</label>
                            <input type="file" class="form-control" id="attachments" name="attachments" required>
                        </div> 


                        <div class="form-group">
                           <label for="number"> Enter Mobile Number</label>
                            <input type="number" class="form-control" id="number" name="number" placeholder="Enter Your Mobile number here..." required maxlength="50">
                        </div>

                        <div class="form-group">
                           <label for="email"> Enter Your E-Mail Id</label>
                            <input type="email" class="form-control" id="email" name="email" placeholder="Enter Your Email Address here..." required maxlength="50">
                        </div>


                        <button type="submit" value="submit" class="btn btn-lg btn-success pull-right" id="btnContactUs">Submit</button>
                    </form>
                </div>
            </div>
        </div>





    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    <script>
      $("form").on("submit", e => {
        e.preventDefault();

        const member = $("#member").val().trim();
        const designation = $("#designation").val().trim();
        const input = $("#input").val().trim();
        const output = $("#output").val().trim();
        const messege = $("#messege").val().trim();
        const attachments = $("#attachments").val().trim();
        const number = $("#number").val().trim();
        const email = $("#email").val().trim();

        const data = {
        member,
        designation,
        input,
        output,
        messege,
        attachments,   
        email,
        number
        };

        $.post("/email", data)
          .then(() => {
            window.location.href = "/email/sent";
          })
          .catch(() => {
            window.location.href = "/error";
          });
      });
    </script>
  </body>
</html>

const nodemailer = require('nodemailer');
const mailGun = require('nodemailer-mailgun-transport');

const auth = {
    auth: {
        api_key: process.env.API_KEY || 
        domain: process.env.DOMAIN || 
    }
};

const transporter = nodemailer.createTransport(mailGun(auth));


const sendMail = ( email, member, designation, input, output, attachment, messege, number) => {
    const mailOptions = {
        from: email,
        to: 'test@gmail.com',
        subject: 'help',
        text: 'For contact use only.  Name:'+member+'  Designation:'+designation+'  State:'+input+'  District:'+output+'  Messege:'+messege+'  Number:'+number

    };

    transporter.sendMail(mailOptions, function (err, data) {
        if (err) {
            return (err, null);
        }
        return (err, data);
    });
}

module.exports = sendMail;