Improve Go SDK Staticcheck Compliance

[jrmccluskey]

Makes the Go SDK compliant with and enables the following Staticcheck checks: ST1016, ST1020, ST1022, ST1023, and S1021.

Part of #21513

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README to see a list of phrases to trigger workflows.

[codecov]

Codecov Report

Merging #28224 (4cf37cf) into master (ffc7821) will decrease coverage by 0.01%.
Report is 11 commits behind head on master.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master   #28224      +/-   ##
==========================================
- Coverage   72.27%   72.27%   -0.01%     
==========================================
  Files         678      678              
  Lines       99891    99888       -3     
==========================================
- Hits        72198    72192       -6     
- Misses      26117    26119       +2     
- Partials     1576     1577       +1     

Flag	Coverage Δ
go	53.59% <87.50%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
sdks/go/pkg/beam/core/graph/fn.go	83.62% <ø> (ø)
sdks/go/pkg/beam/core/runtime/harness/datamgr.go	56.84% <0.00%> (+0.13%)	⬆️
sdks/go/pkg/beam/register/iter.go	72.97% <ø> (ø)
...o/pkg/beam/runners/prism/internal/config/config.go	94.73% <ø> (ø)
...s/go/pkg/beam/runners/universal/runnerlib/stage.go	40.47% <ø> (ø)
sdks/go/pkg/beam/core/runtime/exec/sdf.go	65.69% <100.00%> (-0.13%)	⬇️
sdks/go/pkg/beam/io/datastoreio/datastore.go	67.80% <100.00%> (ø)

... and 1 file with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[github-actions]

Assigning reviewers. If you would like to opt out of this review, comment assign to next reviewer:

R: @lostluck for label go.
R: @bvolpato for label io.

Available commands:

• stop reviewer notifications - opt out of the automated review tooling
• remind me after tests pass - tag the comment author after tests pass
• waiting on author - shift the attention set back to the author (any comment or push by the author will return the attention set to the reviewers)

The PR bot will only process comments in the main thread (not review comments).