title: How to make "Go back to initial StackNavigator Screen when TabNavigator's Tab is pressed"
body: <h3>Intro</h3>
  
  <p>Just like Facebook, Instagram, and any other mobile app, I want to implement 'go back to initial screen in Stacknavigator'</p>
  
  <ol>
  <li>if user press the button,</li>
  <li>it goes back to the very first page. </li>
  </ol>
  
  <h3>Simple Use Case</h3>
  
  <ol>
  <li>see TabNavigator</li>
  <li>Goes to 'Feed' Tab</li>
  <li>Goes to 'User' Screen</li>
  <li>Goes to another 'User' Screen</li>
  <li>PRESS the Main Tab Icon - 'Feed'}</li>
  <li>Goes BACK to 'Feed' Tab // so you won't see the 'back' button</li>
  </ol>
  
  <p>And please leave a comment if you don't understand this use case, I will draw its state flow for you</p>
  
  <p><strong>Code for the icon on my Main TabNavigator.</strong></p>
  
  <pre><code>navigationOptions: ({ navigation }) =&gt; ({
        header: null,
        tabBarIcon: ({ focused }) =&gt; {
            const { routeName } = navigation.state;
            ....
            return (
                &lt;TochableWithoutFeedback onPress={()=&gt;{navigation.goback(iconName)}&gt; 
                // undefined is not a function when I press the Button 
                // deeper screen. (not getting any error on Main)
                    &lt;Ionicons
                        name={iconName}
                        size={30}
                        style={{ marginBottom: -3 }}
                        color={focused ? Colors.tabIconSelected : Colors.tabIconDefault}
                        /&gt;
               &lt;TochableWithoutFeedback&gt;
           );
    },
  </code></pre>