How to fix Ubuntu Server APT UPDATE failure issues

If when attempting to run the 'sudo apt update' command you get error messages like below, simply execute the following commands:

sudo rm -rf /var/lib/apt/lists/*
sudo rm -rf /etc/apt/sources.list.d/*
sudo apt-get update

ERROR MESSAGES:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://dl.yarnpkg.com/debian stable InRelease: The following signatures were invalid: EXPKEYSIG 23E7166788B63E1E Yarn Packaging <yarn@dan.cx>

W: Failed to fetch https://dl.yarnpkg.com/debian/dists/stable/InRelease  The following signatures were invalid: EXPKEYSIG 23E7166788B63E1E Yarn Packaging <yarn@dan.cx>

W: Some index files failed to download. They have been ignored, or old ones used instead.