express投掷错误[err_http_headers_sent]

Question

我真的不知道为什么这样做，谢谢您的帮助！

目的是对cookie和重定向进行身份验证，但截至目前，它的身份验证良好，但没有重定向。

app.get('/admin-login', (req, res) => {
    res.render('admin-login', { title:'Admin login'});
    let key = req.cookies['loggedin']
    if (req.cookies['loggedin']) {
        connection.query('SELECT * FROM sync WHERE key = ?', [key], (error, results, fields) => {
            if (error) {
              return console.error(error.message);
            }
            if (results.length > 0) {
                res.redirect('/home');
            }
          });
    }
}); 

虽然正在抛出这个错误

/home/ubuntu/node_modules/mysql/lib/protocol/Parser.js:437
      throw err; // Rethrow non-MySQL errors
      ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:530:11)
    at ServerResponse.header (/home/ubuntu/nodeprojects/website/node_modules/express/lib/response.js:794:10)
    at ServerResponse.location (/home/ubuntu/nodeprojects/website/node_modules/express/lib/response.js:915:15)
    at ServerResponse.redirect (/home/ubuntu/nodeprojects/website/node_modules/express/lib/response.js:953:18)
    at Query.<anonymous> (/home/ubuntu/nodeprojects/website/app.js:46:16)
    at Query.<anonymous> (/home/ubuntu/node_modules/mysql/lib/Connection.js:526:10)
    at Query._callback (/home/ubuntu/node_modules/mysql/lib/Connection.js:488:16)
    at Query.Sequence.end (/home/ubuntu/node_modules/mysql/lib/protocol/sequences/Sequence.js:83:24)
    at Query._handleFinalResultPacket (/home/ubuntu/node_modules/mysql/lib/protocol/sequences/Query.js:149:8)
    at Query.EofPacket (/home/ubuntu/node_modules/mysql/lib/protocol/sequences/Query.js:133:8) {
  code: 'ERR_HTTP_HEADERS_SENT'