Digital Ocean doesn't have feature which allows one to create automated snapshots of volumes. However, they have REST APIs. And that's all one needs. This project looks for a .env file in the root folder. Here is an example file
# LOG_LEVEL
LOG_LEVEL=info
# Log directory, usually insider /var/log/ for *nix systems
LOG_DIR=/var/log/do-volume-backup-job/
# How many snapshots you want to retain?
SNAPSHOTS_TO_RETAIN=1
# Token
DO_TOKEN=your-top-secret-digital-ocean-get-yours-from-https://cloud.digitalocean.com/account/api/tokens