title: conditionally load different reducers into redux store
body: <p>I have a function that check the role of a user. I want to base on that pass different reducer into a store, is that possible? </p>
  
  <pre><code>import { createStore, applyMiddleware } from 'redux'
  import thunk from 'redux-thunk'
  import { getUserRole } from './utils'
  import { composeWithDevTools } from 'redux-devtools-extension'
  
  import userReducers from './reducers'
  import adminReducers from './reducers/admin'
  
  //share reducer btw member and admin
  let reducers
  if (getUserRole() === 'member') {
    reducers = userReducers
  } else {
    reducers = adminReducers
  }
  
  console.log('reducers', reducers) //undefined unless I refresh the page
  
  const store = createStore(
    reducers,
    composeWithDevTools(
      applyMiddleware(thunk)
    )
  )
  export default store
  </code></pre>
  
  <p>I found a problem, <code>reducers</code> is undefined for the first time (like I login) unless I refresh it.</p>