I installed AWSCLI with homebrew (you don't have to if you don't want)

Adding to your .zshrc

Add aws to you plugins for oh my zsh
Something like this:
plugins=(terraform git aws) NOTE: Terraform and git are there for example.

Then I put this at the bottom.

#Auto tab complete for AWS Cli
export PATH=usr/local/bin/aws_completer:$PATH
autoload -Uz compinit && compinit