Update go1.20

[davidmdm]

Checklist

=========

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have checked for similar issues and haven't found anything relevant.
• This is not a security issue (which should be reported here: https://circleci.com/security/)
• I have read Contribution Guidelines.

Internal Checklist

• I am requesting a review from my own team as well as the owning team
• I have a plan in place for the monitoring of the changes that I am making (this can include new monitors, logs to be aware of, etc...)

Changes

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• update go.mod to use 1.20
• updated build system and ci to use go1.20

Rationale

• Keep go up to date
• Features and libraries the cli depends on will want to use go1.20 (circle-policy-agent for example)