title: ion-nav push method not working in Ionic 4
body: <p><code>&lt;ion-nav&gt;</code> supports push as per the document here -- <a href="https://ionicframework.com/docs/api/nav" rel="nofollow noreferrer">https://ionicframework.com/docs/api/nav</a></p>
  
  <p>My currentPage html (current-page.page.html) has a button component - </p>
  
  <pre><code>&lt;ion-button (click)="goToNextPage()"&gt;Next Page&lt;/ion-button&gt;
  </code></pre>
  
  <p>My currentPage script file (current-page.page.ts) has following code -</p>
  
  <pre><code>import { Component, OnInit } from '@angular/core';
  import { NavController, NavParams } from '@ionic/angular';
  import { NextPage } from '../next-page/next-page.page';
  
  @Component({
    selector: 'current-page',
    templateUrl: './current-page.page.html',
    styleUrls: ['./current-page.page.scss'],
  })
  export class CurrentPage implements OnInit {
  
    constructor(public navCtrl: NavController, public navParams: NavParams) { }
  
    goToNextPage () {
      this.navCtrl.push('NextPage');
    }
  
    ngOnInit() {
    }
  
  }
  </code></pre>
  
  <p>However, I get the format error as <code>Property 'push' does not exist on type 'NavController'</code></p>
  
  <p>Not sure how to use the push method properly. Any help will be appreciated.</p>