first thing first you should get access token from bitly with following instructions:
run following command for installation and refresh your bash session
curl -XGET -o /usr/local/bin/url-shortener https://gist.githubusercontent.com/oksuz/59592679072d503791ee86a284672f85/raw/a2c4f824f56b125819f66fd65413ee2205b0454f/bitly-console.sh && chmod +x /usr/local/bin/url-shortener
then use like url-shortener [url]