Update GoLang to 1.20 & dependency updates

[jamesalfei]

A number of changes have been made as part of this PR which I will summarise below:

• GoLang version has been updated to 1.20 (latest)
• GitHub actions have all been updated to use the latest major versions of all action steps
• Deprecated function usage has been replaced with the corresponding current implementation equivalent
• Various go fmt issues fixed in addition to IntelliJ automated analysis findings

If you would prefer this PR to be broken up and raised as separate requests, please let me know and I'd be more than happy to fulfil that request :)

[tjamet]

Hi!
Thanks for your contribution, those are a lot of changes at once.
Would you mind splitting it into smaller PRs?

Probably:
1 PR for golang update
1 PR for go nodules update
1 PR for actions update
1 PR for cosmetic changes

Thank you

[tjamet]

actually, as part of investigating #200 I envision applying the version updates independently.
I would though encourage you to submit an updated PR with the rest of the changes.