I am encoding Mikrotik Express js Node js and error

app.get('/', (req, res) => {

    

    var listem = ['172.31.1.2', '122.31.2.3']
    listem.forEach(element => {
        var connection = MikroNode.getConnection(element, 'admin', "password..", {
            closeOnDone: false
        });

        var connPromise = connection.getConnectPromise().then(function (conn) {
            var chan1Promise = conn.getCommandPromise('/system/identity/print');
            var chan2Promise = conn.getCommandPromise('/ip/pool/print');
            Promise.all([chan1Promise, chan2Promise]).then(function resolved(values) {
                var val = values[0]
                var vals = values[1]
                console.log('s');
                res.removeHeader('s')
                res.json({ val, vals })


                conn.close();
            }, function rejected(reason) {
                console.log('Oops: ' + reason);
            });
        });
    });
})

CANNOT REMOVE HEADERS AFTER THEY ARE SENT TO THE CL

How can I fix this. How can I export my codes in Promise. Please help me.enter image description here