在http://localhost:9000/testAPI上有一个API调用。
在bin/www：

var port = normalizePort(process.env.PORT || '9000');
app.set('port', port);

在routes/index.js中：

var express = require('express');
var router = express.Router();

/* GET home page. */
router.get('/', function(req, res, next) {
  res.render('index', { title: 'Express' });
});

module.exports = router;

在routes/testAPI.js中：

var express = require('express');
var router = express.Router();
var sqlite3 = require('sqlite3').verbose();
var db = new sqlite3.Database('./db/ocs_athletes.db');

router.get('/', function (req, res, next) {
  db.serialize(function () {
    db.all('SELECT athlete_id, name, surname FROM Athlete', function (
      err,
      row
    ) {
     return res.send(row);
    });
  });

  db.close();
});

module.exports = router;

当运行npm start命令时，API工作，转到http://localhost:9000/testAPI显示包含数据的JSON。
刷新页面时出现问题，提示页面无法访问，终端抛出错误：

GET /testAPI 304 20.628 ms - -
undefined:0


Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:526:11)
    at ServerResponse.header (/home/rares/Documents/Projects/ocsApp/api/node_modules/express/lib/response.js:767:10)
    at ServerResponse.json (/home/rares/Documents/Projects/ocsApp/api/node_modules/express/lib/response.js:264:10)
    at ServerResponse.send (/home/rares/Documents/Projects/ocsApp/api/node_modules/express/lib/response.js:158:21)
    at Statement.<anonymous> (/home/rares/Documents/Projects/ocsApp/api/routes/testAPI.js:12:11)
    at Statement.replacement (/home/rares/Documents/Projects/ocsApp/api/node_modules/sqlite3/lib/trace.js:25:27) {
  code: 'ERR_HTTP_HEADERS_SENT'
}
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! api@0.0.0 start: `node ./bin/www`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the api@0.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

有办法解决这个问题吗？