[Golang][client] fix RFC-3339 date-time query param

[grokify]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
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@antihax
@bvwells

Description of the PR

Resubmitting #325

I just used 3.1.0 to regenerate the go-ringcentral client and noticed that while this was previously merged, the issue persists in the release or master branch.

It was merged into 3.1.x and mentioned on release page, but did not get into the actual file.

• Release: https://github.com/OpenAPITools/openapi-generator/releases/tag/v3.1.0
• 3.1.0 File 100ec44: https://github.com/OpenAPITools/openapi-generator/blob/100ec449fe45176fc5479af078d02b80f855838c/modules/openapi-generator/src/main/resources/go/client.mustache

[wing328]

@grokify thanks again for the PR but after reviewing the git log, I still have no clue how this could have happened. I'll use "git bisect" tomorrow to see if I can figure out what's wrong.

Merging this fix into master for the time being.

[wing328]

UPDATE: the original change was rolled back by 478b0d6#diff-2faebed03061f084b33bf45cb4397690.

I'm reviewing other changes in that commit to see what else has been rolled back.

[wing328]

Only 2 PRs (merged before Jun 19) were rolled back

• Eliminate MySQL dependency of Rails 5 stub server Eliminate MySQL dependency of Rails 5 stub server #279
• [Golang][client] fix RFC-3339 date-time query param [Golang][client] fix RFC-3339 date-time query param #325

Both have been added back to the latest master.