Passing Data Using React-Native Navigation

Im trying to pass data between screens in my app. Currently I am using

"react-native": "0.46.0","react-navigation": "^1.0.0-beta.11"

I have my index.js

 import React, { Component } from 'react';    import {      AppRegistry,    } from 'react-native';    import App from './src/App'    import { StackNavigator } from 'react-navigation';    import SecondScreen from './src/SecondScreen'    class med extends Component {      static navigationOptions = {        title: 'Home Screen',      };      render(){        const { navigation } = this.props;        return (<App navigation={ navigation }/>        );      }    }    const SimpleApp = StackNavigator({      Home: { screen: med },      SecondScreen: { screen: SecondScreen, title: 'ss' },        });    AppRegistry.registerComponent('med', () => SimpleApp);

app as

    import React, { Component } from 'react';    import {      StyleSheet,      Text,      Button,      View    } from 'react-native';    import { StackNavigator } from 'react-navigation';    const App = (props)  => {      const { navigate } = props.navigation;      return (<View><Text>            Welcome to React Native Navigation Sample!</Text><Button              onPress={() => navigate('SecondScreen', { user: 'Lucy' })}              title="Go to Second Screen"            /></View>      );    }    export default App

then in the secondscreen.js where we will fetch the data which passed from the previous screen as

    import React, { Component } from 'react';    import {      StyleSheet,      Text,      View,      Button    } from 'react-native';    import { StackNavigator } from 'react-navigation';    const SecondScreen = (props)  => {      const { state} = props.navigation;      console.log("PROPS"+ state.params);      return (<View><Text>            HI</Text></View>      );    }    SecondScreen.navigationOptions = {      title: 'Second Screen Title',    };    export default SecondScreen

Whenever I console.log I get undefined.
https://reactnavigation.org/docs/navigators/navigation-propThe docs say every screen should have these values what am I doing wrong?