title: how to fix this.backgroundMode.unlock() when not working
body: <p>i using ionic4</p>
  
  <p>i import
  ionic cordova plugin add cordova-plugin-background-mode
  npm install @ionic-native/background-mode</p>
  
  <p>in my project</p>
  
  <p>i using code </p>
  
  <pre><code>   ....
     import { BackgroundMode } from '@ionic-native/background-mode/ngx';
     ....
     private backgroundMode: BackgroundMode,
     ....
     this.backgroundMode.enable();
     this.backgroundMode.isScreenOff( () =&gt; {
      alert('screen off');
      this.backgroundMode.unlock();
     });
  </code></pre>
  
  <p>when my phone is turn off screen not work
  weackup and unlock</p>
  
  <p>or testing by </p>
  
  <pre><code>   ....
     import { BackgroundMode } from '@ionic-native/background-mode/ngx';
     ....
     private backgroundMode: BackgroundMode,
     ....
     this.backgroundMode.enable();
     this.backgroundMode.isScreenOff( () =&gt; {
      alert('screen off');
      this.backgroundMode.wakeUp();
      this.backgroundMode.unlock();
     });
  </code></pre>
  
  <p>or</p>
  
  <pre><code>....
     import { BackgroundMode } from '@ionic-native/background-mode/ngx';
     ....
     private backgroundMode: BackgroundMode,
     ....
     this.backgroundMode.enable();
     this.backgroundMode.isScreenOff( function(bool) {
      if (bool) {
       alert('screen off');
       this.backgroundMode.wakeUp();
       this.backgroundMode.unlock();
      }else{
       alert('screen on');
      }
     });
  </code></pre>
  
  <p>or</p>
  
  <pre><code>....
     import { BackgroundMode } from '@ionic-native/background-mode/ngx';
     ....
     private backgroundMode: BackgroundMode,
     ....
     this.backgroundMode.enable();
     this.backgroundMode.isScreenOff( function(bool) {
       this.backgroundMode.wakeUp();
       this.backgroundMode.unlock();
     });
  </code></pre>
  
  <p>or</p>
  
  <pre><code>   ....
     import { BackgroundMode } from '@ionic-native/background-mode/ngx';
     ....
     private backgroundMode: BackgroundMode,
     ....
     this.backgroundMode.enable();
     this.backgroundMode.wakeUp();
     this.backgroundMode.unlock();
  </code></pre>
  
  <p>and BackgroundMode add provider in app.moudel.ts</p>
  
  <p>but not working in all way
  but working code </p>
  
  <pre><code>   this.backgroundMode.moveToForeground();
     this.backgroundMode.moveToBackground();
  </code></pre>
  
  <p>how to fix for using this.backgroundMode.wakeUp(); and this.backgroundMode.unlock(); for when turn off screen my device or my phone?</p>
  
  <p>thanks</p>