In my nextjs/firebase app, everything seems to work in local (dev mode), but when i run npm generate, my collection articles doesn't get built at all..

Here is my firebase js code

import { initializeApp } from 'firebase/app';
import { getFirestore, collection, getDocs } from 'firebase/firestore';

const firebaseConfig = {

}

// init app
initializeApp(firebaseConfig);

// init services
const db = getFirestore();

// collection ref
const colRef = collection(db, 'articles');

let posts = [];

export const getPosts = async () => {
// get collection data
getDocs(colRef)
.then((snapshot) => {
  snapshot.docs.forEach((post) => {
    posts.push({ ...post.data()})
  })
})
.catch(err => {
  console.log(err.message)
})
return posts;
}

And this is the way i call it in my index js file:

export async function getStaticProps() {
  const posts = await getPosts();
  return {
    props: {
      posts,
    },
  };
}