doctl is the digitalocean cli tool for interfacing with digitalocean resources via CLI.
It has completion options built-in, for example you can run this command to enable bash completion
doctl completion bash > /etc/bash_completion.d/doctl(may need to sudo tee the right side)
But I have been unable to figure out how to get autocompletion for fish shell working.
The doctl cli does not provide the syntax or example command.
I tried this, but it doesn't work
doctl completion fish > .config/fish/completions/doctl