As you can see, this is way less code than rollback.go

new_user_rollback.go

import "github.com/frikky/firestore-rollback-go"

// This is our self-defined fields.
// FirestoreEvent.Value.Fields = User
type User struct {
	Username   rollback.StringValue  `json:"userId"`
	Email      rollback.StringValue  `json:"email"`
	DateEdited rollback.IntegerValue `json:"date_edited"`
}

// Handles the rollback of any previous document
func handleRollback(ctx context.Context, e FirestoreEvent) error {
	// writtenData, firestoreReturn, err :=
	_, _, err := rollback.Rollback(
		ctx,
		client,            // Your firestore client
		e.OldValue.Name,   // The path to roll back
		e.OldValue.Fields, // The parsed data you have
	)

	return err
}