Yarn Package invalid key

If your environment has failed due to an issue with the yarn package, similar to below, it means there's an issue with the package's GPG signature. 

GPG error: https://dl.yarnpkg.com/debian stable InRelease: The following signatures 
were invalid: EXPKEYSIG 23E7166788B63E1E Yarn Packaging <yarn@dan.cx>

This can be resolved by adding following to the top of your environment's Dockerfile to refresh the package key:  

RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add - 

Alternatives - which can happen depending on your specific version or date:

RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | gpg --dearmor | sudo tee /usr/share/keyrings/yarnkey.gpg >/dev/null

Or if you do not have any success with apt-key (it is becoming deprecated) the use this:

ENV YARNKEY=yarn-keyring.gpg
RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo gpg --dearmour -o /usr/share/keyrings/$YARNKEY && \
  echo "deb [signed-by=/usr/share/keyrings/$YARNKEY] https://dl.yarnpkg.com/debian stable main" | sudo tee /etc/apt/sources.list.d/yarn.list

These are 'best effort' suggestions and have been verified to work in a standard environment.

If you're seeing a similar error but for an nvidia key, please check out this article: Build error for nvidia GPG key