sem: fix goleak

[hawkingrei]

What problem does this PR solve?

Issue Number: close #46844

Problem Summary:

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[hawkingrei]

/check-issue-triage-complete

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Defined2014, xhebox

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• OWNERS [Defined2014,xhebox]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-09-11 04:24:18.694782167 +0000 UTC m=+243240.619338557: ☑️ agreed by xhebox.
• 2023-09-11 04:24:32.785306224 +0000 UTC m=+243254.709862620: ☑️ agreed by Defined2014.

[codecov]

Codecov Report

Merging #46845 (039be20) into master (262327f) will decrease coverage by 0.6046%.
Report is 4 commits behind head on master.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #46845        +/-   ##
================================================
- Coverage   73.3236%   72.7190%   -0.6046%     
================================================
  Files          1322       1343        +21     
  Lines        396478     402765      +6287     
================================================
+ Hits         290712     292887      +2175     
- Misses        87245      91314      +4069     
- Partials      18521      18564        +43     

Flag	Coverage Δ
integration	27.7455% <ø> (?)
unit	73.3402% <ø> (+0.0166%)	⬆️

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

Components	Coverage Δ
dumpling	54.0444% <ø> (ø)
parser	84.9717% <ø> (+0.0107%)	⬆️
br	48.3115% <ø> (-4.3162%)	⬇️