Dynamic parameter not working ionic-v4

Ionic Framework
1

This is not working

opennext(cid){
var np = '/contract/'+cid;
this.navCtrl.goForward(np);
}

but this is working

opennext(cid){
  this.navCtrl.goForward('/contract/53');
}

error is

core.js:1633 ERROR Error: Uncaught (in promise): Error: Cannot match any routes. URL Segment: 'contract'
Error: Cannot match any routes. URL Segment: 'contract'
2

more code would be helpful here…