The etcd backup script fails to generate a backup

Issue

When attempting to create a backup snapshot of the etcd database, the /usr/local/bin/etcd-snapshot-backup.sh script finishes after only a few lines of output without showing any error:

sudo -E /usr/local/bin/etcd-snapshot-backup.sh ./assets/backup/snapshot.db
Creating asset directory ./assets
Downloading etcdctl binary..

Furthermore, the generated ./assets/backup directory is empty.

$ ls
assets  root-supporting-mandiri.crt
$ ls -ltr assets/backup/
total 0

The expected output of the script should be longer (example below):

sh-4.4# sudo -E /usr/local/bin/etcd-snapshot-backup.sh ./assets/backup/snapshot.db
Creating asset directory ./assets
Downloading etcdctl binary..
etcdctl version: 3.3.10
API version: 3.3
Trying to backup etcd client certs..
etcd client certs found in /etc/kubernetes/static-pod-resources/kube-apiserver-pod-2 backing up to ./assets/backup/
Backing up /etc/kubernetes/manifests/etcd-member.yaml to ./assets/backup/
Snapshot saved at ./assets/backup/snapshot.db