我正在尝试使用Nodemailer和OAuth2发送电子邮件。它在localhost上工作，但在Heroku上不工作，因此，我将OAuth添加到Nodemailer createTransport。但现在它甚至在localhost上也不工作。
我的代码是：

const oAuth2Client =new google.auth.OAuth2(process.env.CLIENT_ID,process.env.CLIENT_SECRET,process.env.REDIRECT_URI);
oAuth2Client.setCredentials({refresh_token:process.env.REFRESH_TOKEN});

const sendMail =async(email,code)=>{
    try
    {const accessToken = await oAuth2Client.getAccessToken();
    let transport = nodemailer.createTransport(smtTransport({
        service: "gmail",
        auth: {
            type:"OAuth2",
            user: "kediaarts@gmail.com",
            pass: process.env.EMAIL_PASS,
            clientId:process.env.CLIENT_ID,
            clientSecret:process.env.CLIENT_SECRET,
            refreshToken:process.env.REFRESH_TOKEN,
            accessToken:accessToken
        }
    }));

    let mailOptions,link;

   link = "http://localhost:5000"+email+"/"+code.toString() ;
    mailOptions={
        from:'"Horizons" <no-reply@gmail.com>',
        to : email,
        subject: "Please verify your Email",
        html : "<h1>Horizons</h1><br><h2>Hi,<br> Please click on the link to verify your email.</h2><br><a href="+link+">Click here to verify</a>",
    }
    const result =await transport.sendMail(mailOptions);
    return result;

} catch(error){
    console.log(error);
}

}

出现以下错误：

Error: No refresh token or refresh handler callback is set.
    at OAuth2Client.getAccessTokenAsync (E:\horizons_blog\node_modules\google-auth-library\build\src\auth\oauth2client.js:224:27)
    at OAuth2Client.getAccessToken (E:\horizons_blog\node_modules\google-auth-library\build\src\auth\oauth2client.js:209:25)
    at sendMail (file:///E:/horizons_blog/controllers/user.js:14:45)      
    at signUp (file:///E:/horizons_blog/controllers/user.js:78:9)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)