问Koa2发送404，尽管function工作正常。怎么回事？

EN

module.exports = {

/**
 *@api {post} /contact
 *@apiGroup Public
 * @apiName sendMail
 * @apiParam {String} [name] User needs to provide their name
 * @apiParam {String} [email] User needs to provide their email
 * @apiParam {String} [message] user needs to provide their message
 * @apiParamExample {String} Request Params :
 * {
 *  "name"  : "Cello",
 *  "email" : "yo@yo.ma,
 *  "message" : "you are so great"
 * }
 * @apiSuccess {Object} return value  A success or failure
 * @apiSuccessExample {json} Response:
 * {
 *  "result" : "success"
 *  "callback" : "Do something"
 * }
 * @apiExample {curl} Example usage:
 * curl -i http://localhost:4000/contact
 * @apiDescription Any user can submit contact
 * @apiHeader {String} Authorization  JWT Authorization header (optional)
 * @apiHeaderExample {json} Request Authorization Header
 * {
 *  "authorization" : "jkahdkjashdk324324342"
 * }
 */
async mail(ctx){
let {email, name, message} = ctx.request.body;

if (!email) {
    ctx.throw(400, 'please provide the email')
}
if (!name) {
    ctx.throw(400, 'please provide a name')
}
if (!message) {
    ctx.throw(400, 'please provide a message')
}
var api_key = 'key-xxxxxxxxxx';
var domain = 'mg.domain.com';
var mailgun = require('mailgun-js')({apiKey: api_key, domain: domain});

var data = {
    from: name+'<'+email+'>',
    to: 'me@domain.com',
    subject: 'Contact Form',
    text: message
};

var result = mailgun.messages().send(data, function (error, body) {
    console.log(body);
});