node.js Error: EACCES: permission denied, open 'privkey.pem'

Question

I'm setting secure websocket over node.js using socket.io:

var fs = require('fs');
var https = require('https');
var server = https.createServer({ 
    key: fs.readFileSync("/etc/letsencrypt/live/host/privkey.pem"),
    cert: fs.readFileSync("/etc/letsencrypt/live/host/fullchain.pem") 
});
server.listen(3000);
var io = require('socket.io').listen(server);
io.sockets.on('connection', function(socket) {
....

And when run server:

user@admin:/var/www/host/node.js_ws$ node server.js

I'm getting

node:internal/fs/utils:344
    throw err;
    ^

Error: EACCES: permission denied, open '/etc/letsencrypt/live/host/privkey.pem'

I already sudo chmod / chown 755 the folder and pem files there, but no chance. Where is my bad?