client_boot.js

import storeModule from './store-module';

export default async ({ Vue, router, store }) => {
  Vue.use(storeModule, router, store, {
    preserveState: preserveState
  });
}

componentThatFetch.vue

<template>
  <q-page padding>
    <div>refresh and '$store.state.storeModule' won't exist</div>
    {{$store.state.storeModule ? JSON.stringify($store.state.storeModule) : 'not there, placeholder'}}
  </q-page>
</template>

<script>
export default {
  name: 'ComponentThatFetch',
  serverPrefetch () {
    this.$store.dispatch({
			type: 'storeModule/addData',
			data: {test: 'testData'}
		});
  },
}
</script>

server_boot.js

import storeModule from './store-module';

export default async ({ Vue, router, store, ssrContext }) => {
  Vue.use(storeModule, router, store, {
    request: ssrContext.req
  });
}

store-module.js

let storeModule = {
	namespaced: true,
	state: () => ({
		data: {}
	}),
	mutations: {
		SET_DATA(state, payload) {
			state.data = payload.data;
		}
	},
	actions: {
		setData(context, payload) {
			context.commit({
				type: 'SET_DATA',
				data: payload.data
			});
		}
	}
};

export default {
  install: function install(Vue, router, store, options) {
    //do_stuff_with(router, options.request)
    store.registerModule('storeModule', storeModule, {preserveState: options.preserveState});
  }
};