fix: use redis Close() instead of Shutdown()

[seanlion]

What was the problem

• The Redis retriever's Shutdown() method was calling client.Shutdown(ctx), which sends a Redis SHUTDOWN command to the server. This command is intended to shut down the entire Redis server, not just close the client connection.
• Missing error handling: The error from the shutdown call was ignored

Changes

• Replaced client.Shutdown(ctx) with client.Close() to only close the client connection
• Added nil check to handle shutdown before initialization
• Set client to nil after closing to prevent reuse
• Ignore redis.ErrClosed errors for idempotency

Why Close() instead of Shutdown():

• Close(): Closes the client connection pool
• Shutdown(): Sends SHUTDOWN command to Redis server

How to test the change

• Added Test_Redis_Shutdown with test cases.

Related Issue

#4139

Checklist

• I have tested this code
• I have added unit test to cover this code
• I have updated the documentation (README.md and /website/docs)
• I have followed the contributing guide

[netlify]

✅ Deploy Preview for go-feature-flag-doc-preview canceled.

Name	Link
🔨 Latest commit	c15c70c
🔍 Latest deploy log	https://app.netlify.com/projects/go-feature-flag-doc-preview/deploys/68fdf249ae722300085ab7c1

[seanlion]

/gemini review

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.93%. Comparing base (a027586) to head (c15c70c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4140      +/-   ##
==========================================
+ Coverage   84.83%   84.93%   +0.10%     
==========================================
  Files         139      138       -1     
  Lines        5677     5643      -34     
==========================================
- Hits         4816     4793      -23     
+ Misses        651      644       -7     
+ Partials      210      206       -4     

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[gemini-code-assist]

Code Review

This pull request correctly addresses a critical issue by replacing client.Shutdown() with client.Close(), preventing the accidental shutdown of the entire Redis server. The changes are robust, incorporating nil checks, setting the client to nil after closing to prevent reuse, and handling redis.ErrClosed for idempotency. The accompanying tests are thorough and cover the new logic well. I have provided a few suggestions to enhance code clarity and consistency.

[thomaspoignant]

Hey @seanlion thanks a lot for this catch, I will merge this change and it will be part of the next release.

I've added some tests to validate all the cases of the shutdown function.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[seanlion]

Hey @seanlion thanks a lot for this catch, I will merge this change and it will be part of the next release.

I've added some tests to validate all the cases of the shutdown function.

@thomaspoignant Thanks for review!