fix: avoid data race when watching request cancellation

[beck-8]

[2026-03-18 23:43:57] [08a61818] [info ] [gin_logger.go:93] 200 |       11.694s |       127.0.0.1 | POST    "/v1/responses"
[2026-03-18 23:44:02] [2b7669ad] [info ] [gin_logger.go:93] 200 |        4.712s |       127.0.0.1 | POST    "/v1/responses"
panic: interface conversion: interface {} is , not chan struct {}

goroutine 2426 [running]:
context.(*cancelCtx).Done(0x0?)
        /opt/hostedtoolcache/go/1.26.1/x64/src/context/context.go:451 +0x1a5
github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers.(*BaseAPIHandler).GetContextWithCancel.func1()
        /home/runner/work/CLIProxyAPI/CLIProxyAPI/sdk/api/handlers/handlers.go:347 +0x49
created by github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers.(*BaseAPIHandler).GetContextWithCancel in goroutine 2594
        /home/runner/work/CLIProxyAPI/CLIProxyAPI/sdk/api/handlers/handlers.go:343 +0x290

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical data race within the context cancellation mechanism, which previously caused a panic during concurrent request processing. The fix ensures that the context used for cancellation monitoring is correctly captured, thereby preventing unexpected runtime errors and improving the stability of API request handling.

Highlights

• Data Race Fix: Addressed a data race condition that could lead to a panic during request cancellation by capturing the context.Context in a local variable before launching a goroutine.

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[gemini-code-assist]

Code Review

This pull request fixes a data race that occurs when watching for request cancellation. The race happens because the newCtx variable was being modified after being captured by a goroutine. The fix introduces a new variable cancelCtx to be used by the goroutine, which resolves the issue. I've added a suggestion to use a more idiomatic Go pattern for passing variables to goroutines, which can further improve code clarity and safety.

[gemini-code-assist]

While this change correctly fixes the data race, a more idiomatic Go approach is to pass newCtx as an argument to the goroutine. This makes the variable capture explicit and is a safer pattern for concurrent code, as it avoids potential confusion with closure variable capturing.

	if requestCtx != nil && requestCtx != parentCtx {
		go func(ctxToWatch context.Context) {
			select {
			case <-requestCtx.Done():
				cancel()
			case <-ctxToWatch.Done():
			}
		}(newCtx)
	}

References

1. To prevent data races when using variables inside a goroutine, it's a best practice to pass them as arguments to the goroutine's function. This creates a copy of the variable for the goroutine, ensuring it doesn't get affected by modifications in the parent goroutine.

[luispater]

Summary:
This PR fixes a real concurrency bug in GetContextWithCancel by avoiding closure capture of a context interface variable that is later reassigned. The change is minimal, scoped, and matches the reported panic stack.

Key findings:

• Blocking: none.
• Non-blocking: add a focused regression test to lock in the race fix over time.

Why this looks correct:

• Before: the goroutine selected on newCtx.Done() while newCtx was subsequently reassigned via context.WithValue(...), which can race on the captured interface variable.
• After: the goroutine selects on cancelCtx.Done() where cancelCtx is a stable snapshot of the cancelable context returned by context.WithCancel, removing the variable-capture race hazard.

Test plan:

• CI build check is passing.
• I did not run local tests in this review pass.
• Suggested follow-up: add a targeted stress/race test around this function (go test -race).

Overall:
The fix is appropriate and low risk. I recommend approve.

This is an automated Codex review result and still requires manual verification by a human reviewer.