Redux Error Actions must be plain objects. Use custom middleware for async actions

I am new to redux and I am stuck in an error, while dispatching an action I am getting error

"Actions must be plain objects. Use custom middleware for async actions.", I have checked the flow but can't see any problem,here's below code"

My JS container File:

import React from 'react'
import {Redirect} from 'react-router-dom'
import * as actions from './../store/actions/index'
import { connect } from 'react-redux'

class home extends React.Component{

constructor(props){
    super(props);
    this.state={
        isClk:false
    }
}


performLogout = (evt)=> {
    evt.preventDefault();
    this.props.onLogout();
    this.setState({isClk: true})
};

render(){

    let redirect=null;

    if (this.state.isClk){
        redirect=<Redirect to="/login"/>
    }
    return(

        <div>
            {redirect}
            <h1>In Home</h1>
            <button onClick={this.performLogout}>Logout</button>
        </div>
    )
}

}

  const mapDispatchToProps = dispatch =>{
     return {
      onLogout: () => dispatch(actions.logout())
    }
  };

 export default connect(null,mapDispatchToProps)(home)

Index.js:

   export {
auth,
logout
} from './auth'

Actions(auth.js):

export const logout =()=>{
 return(
    actionTypes.AUTH_LOGOUT
 )
};

Reducers:

  const authLogout=(state,action)=>{
     return updateObject(state,{
         token:null,
         loading:false,
         error:null
    })
   };

 const reducer=(state=initialState,action)=>{

 switch(action.type){
    case actionTypes.AUTH_FAIL: return authFail(state,action);
    case actionTypes.AUTH_LOGOUT: return authLogout(state,action);
    default:
        return state
  }

 };

Store:

       import {Provider} from 'react-redux'
       import { createStore, applyMiddleware, compose, combineReducers } from 'redux'
       import {BrowserRouter} from "react-router-dom";
       import authReducer from './Containers/store/reducers/auth'
       import thunk from 'redux-thunk';

       const composeEnhancers = compose;

       const RootReducer=combineReducers({
              auth:authReducer
       });

       const store=createStore(RootReducer,composeEnhancers(applyMiddleware(thunk)));

       const app = (
                      <Provider store={store}>
                     <BrowserRouter>
                       <App />
                     </BrowserRouter>
                      </Provider>
                  );

ReactDOM.render(app, document.getElementById('root'));

I want to perform logout action when user click on logout button,I can get where the problem, Is my store is properly initialized or any problem in thunk? or anyother maybe while dispatching, kindly guide?