let store = new Vuex.Store({
    state: {
        user: null,
    },

    mutations: {
        setUser: function (state, user) {
            state.user = user;
        },

<p v-if="!this.$store.state.user">Waiting...</p>

async function checkUserSession() {
    return axios.get("/api/user").then(async (response) => {
        store.commit('setUser', response.data.data);
    }).catch(async (error) => {
        store.commit('setUser', null);
    });
}

router.beforeEach(async (to, from, next) => {
    if (!store.state.user) {
        await checkUserSession();
    }