build: update go version to 1.18

[asraa]

Signed-off-by: Asra Ali asraa@google.com

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Fixes #307
Release Notes:

Types of changes:

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Description of the changes being introduced by the pull request:
Updates go version to 1.18.

Do we want to continue to test previous go versions?

Please verify and check that the pull request fulfills the following requirements:

• Tests have been added for the bug fix or new feature
• [ x ] Docs have been added for the bug fix or new feature

[asraa]

@rdimitrov does this address #301 with the content in TESTING.md? Mostly my incompatibility is due to python-tuf being at version .20. We should update that too

[znewman01]

Mostly my incompatibility is due to python-tuf being at version .20. We should update that too

#228 should do that (issue #221). It was blocked on #232, which #310 should fix. Once #310 is in I'll rebase

[asraa]

#228 should do that (issue #221). It was blocked on #232, which #310 should fix. Once #310 is in I'll rebase

Thank you! That's perf, closed that issue.

[rdimitrov]

@rdimitrov does this address #301 with the content in TESTING.md? Mostly my incompatibility is due to python-tuf being at version .20. We should update that too

It does! Thank you! 🙏