ios – Firestore Database Question

I copied and pasted the documentation from Firestore:

personal func getMultipleAll() async {
   // [START get_multiple_all]
   do {
       let querySnapshot = strive await self.db.assortment("cities").getDocuments()
     for doc in querySnapshot.paperwork {
       print("(doc.documentID) => (doc.information())")
     }
   } catch {
     print("Error getting paperwork: (error)")
   }
   // [END get_multiple_all]
 }

This is the hyperlink: https://firebase.google.com/docs/firestore/query-data/get-data?hl=en&authuser=0

Each time I attempt to run this it crashes and goes to the App Delegate. It is copied and pasted from google. Any assist?