Use Yubikey authenticator to set up a challenge-response algorithm in slot 2 of your Yubikey. Then, make sure you have the command line tool ykchalresp installed. It usually comes packaged with the Yubikey personalization tool, e.g. on macOS via Homebrew:

brew install ykpers

Then, use the command to read a string from stdin and hash it with the challenge-response credential in slot 2 of your Yubikey:

ykchalresp -2 -i-

After entering your string, press CTRL-D twice, and touch your Yubikey. This will generate the hash.