gatsby-ssr.js

import React from 'react';
import { Provider } from 'react-redux';
import { renderToString } from 'react-dom/server';

import createStore from './src/store';

const store = createStore();

exports.replaceRenderer = ({ bodyComponent, replaceBodyHTMLString }) => {

    function renderConnectedBody(reduxStore) {
        return (
            <Provider store={ reduxStore }>
                { bodyComponent }
            </Provider>
        );
    }

    const providerWrappedBodyString = renderToString(
        renderConnectedBody(store)
    );

    replaceBodyHTMLString(providerWrappedBodyString);
};