[1058] Generate hangs with fetch from Firebase to store

// pages/index.vue

// ...SNIP...

fetch({ store }) {
  return firebase.database().ref('/').once('value')
    .then((snap) => {
      return store.dispatch('setDataAction');
    });
}

// store/index.js

import Vuex from 'vuex'

const store = () => new Vuex.Store({
  state: {
    data: null,
  },
  mutations: {
    setDataMutation(state, _data) {
      state.data = _data;
    }
  },
  actions: {
    setDataAction({commit}, _data) {
      return new Promise((resolve, reject) => {
        commit('setDataMutation', _data);
        resolve();
      });
    },
  },
})

export default store

Hangs after executing nuxt generate:

...
  nuxt:generate Generate file: /index.html +906ms
  nuxt:generate HTML Files generated in 12.6s +1ms
[nuxt] Generate done      # <----- Hangs here