fix: race condition in Retry function

[deblasis]

This PR introduces a test to repro the data race issue and also the fix for it in a separate commit.

Issue discovered in getsops/sops integration tests.
Related: getsops/sops#1226
Failed job: https://github.com/getsops/sops/actions/runs/18238383955/job/51962367579?pr=1226

How to Review

Step 1: Reproduce the Bug (Commit f38c967)

# Checkout the first commit (test only, no fix)
git checkout f38c967789

# Run test with race detector
cd common
go test -race -run TestRetry_RaceCondition

# Expected output (BUGGY):
# WARNING: DATA RACE
# Write at 0x... by goroutine X: retry.go:871
# Previous read at 0x... by goroutine Y: retry.go:907
# Found 1 data race(s)
# exit status 66
# FAIL

Step 2: Verify the Fix (Commit 7770835)

# Checkout the fix commit
git checkout 7770835982

# Run same test with race detector
cd common
go test -race -run TestRetry_RaceCondition

# Expected output (FIXED):
# PASS
# ok    github.com/oracle/oci-go-sdk/v65/common 1.020s
# ✅ No race detected!

Step 3: Run Full Test Suite

# Run all common package tests with race detector
go test -race ./common/ -v

# Run broader test suite
go test -race ./... -short

Problem Description

Root Cause

The Retry function had a data race when the context was cancelled:

// Line 807: Shared variable
var response OCIResponse
var err error

go func() {
    // Line 871: Goroutine WRITES to response
    response, err = operation(ctx, request, rsc, extraHeaders)
    // ...
}()

// Lines 905-910: RACE CONDITION
select {
case <-ctx.Done():
    // Line 907: Main thread READS response (concurrent access!)
    return response, ctx.Err()
case result := <-retrierChannel:
    return result.response, result.err
}

Impact

• Data Race: Undefined behavior per Go memory model
• Panic Risk: nil pointer dereference when accessing response fields
• Production Impact: Discovered in getsops/sops integration tests

Original Error

panic: runtime error: invalid memory address or nil pointer dereference
at github.com/oracle/oci-go-sdk/v65/common.newServiceFailureFromResponse
    common/errors.go:111

Solution

Changes Made

The fix ensures the retry goroutine checks for context cancellation and exits promptly:

1. Added context check before each retry attempt
2. Made sleep interruptible
3. Removed the racing select statement

Signed-off-by: Alessandro De Blasis alex@deblasis.net

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