// App.js
import { NavigationActions } from 'react-navigation';
import AppNavigator from './navigation/AppNavigator';

<AppNavigator
          ref={
            (navigatorRef) => {
              navigatorRef.dispatch(
                NavigationActions.navigate({
                  routeName: 'Main',
                }),
              );
            }
          }
        />



// AppNavigator.js
import { createAppContainer, createSwitchNavigator } from 'react-navigation';
import MainTabNavigator from './MainTabNavigator';
import AuthTabNavigator from './AuthTabNavigator';

export default createAppContainer(
  createSwitchNavigator({
    Main: MainTabNavigator,
    Auth: AuthTabNavigator,
  },
  {
    initialRouteName: 'Auth',
  })
);