Implement caching in Go CI workflow

[JaclynCodes]

Added caching step to GitHub Actions workflow for Go.

[google-cla[bot]]

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[JaclynCodes]

@copilot open a new pull request to apply changes based on the comments in this thread

[JaclynCodes]

@copilot open a new pull request to apply changes based on the comments in this thread

[puellanivis]

Thank you for your interest into contributing to this project.

Unfortunately this project does not accept GitHub pull requests as the source-of-truth for this project is hosted at https://go.googlesource.com/protobuf. This project page on GitHub is a mirror of that other repository.

If you would like to contribute to this project, please follow the contribution guidelines for instructions on how to send a change. If the change you'd like to make is more substantial or introduces any new features, then it should first be discussed on the issue tracker.