_http_outgoing.js:470
    throw new ERR_HTTP_HEADERS_SENT('set');
    ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:470:11)
    at Array.write (/media/selin/Data/Documents/WORK/My Projects/Web Developing/GitHub/IgorZaviryukhaA2Lab/lesson_5/5-2_News/node_modules/finalhandler/index.js:285:9)
    at listener (/media/selin/Data/Documents/WORK/My Projects/Web Developing/GitHub/IgorZaviryukhaA2Lab/lesson_5/5-2_News/node_modules/on-finished/index.js:169:15)
    at onFinish (/media/selin/Data/Documents/WORK/My Projects/Web Developing/GitHub/IgorZaviryukhaA2Lab/lesson_5/5-2_News/node_modules/on-finished/index.js:100:5)
    at callback (/media/selin/Data/Documents/WORK/My Projects/Web Developing/GitHub/IgorZaviryukhaA2Lab/lesson_5/5-2_News/node_modules/ee-first/index.js:55:10)
    at IncomingMessage.onevent (/media/selin/Data/Documents/WORK/My Projects/Web Developing/GitHub/IgorZaviryukhaA2Lab/lesson_5/5-2_News/node_modules/ee-first/index.js:93:5)
    at IncomingMessage.emit (events.js:182:13)
    at endReadableNT (_stream_readable.js:1094:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)

const
    express    = require('express'),  //include express module
    Url        = require('url'),    //include url module
    bodyParser = require('body-parser'),  //for post requests
    mysql      = require('mysql'),  //include mySQL module
    app        = express(),   //server

    connection = mysql.createConnection({  //connecting to database
        host: '127.0.0.1',  //ip adress
        user: 'admin',  //name of user in mySQL
        password: '123',  //user password
        database: 'news'  //database name
    });

connection.connect(function(err) {  //establishing connecting to DB
    if (err) throw err;   //if we have some exception
    console.log('Connected!');  //if everything is OK
});

app.set('view engine', 'ejs');  //connect ejs to application
app.use('/public', express.static('public'));  //using static folder for css and more
app.use(bodyParser.urlencoded({ extended: true })); //using body parser for POST requests

//generate root page for user
app.get('/', function(request,response) {
    connection.query('SELECT title, text, date FROM news', function(err, result) {
        if (err) throw err;
        response.render('index', { posts: result });
        response.end();
    });
});

app.post('/', function(request, response) {
    connection.query('SELECT password FROM moderator', function(err, result) {
        if (err) throw err;
        if (!req.body) return sendStatus(400);
        var password = result[0].password;

        if (password === request.body.password) {
            response.render('index', { moderator: true });
            response.end();
        } else {
            response.render('index', { moderator: false });
            response.end();
        }
    });
});

app.listen(8080);  //listening to the port

response.render('index', { moderator: true });

response.render('index', { moderator: false });