fix ticker stop race condition by clearing period before removing timer

[cataggar]

The job failed during the TestBuild/ARM64Linux/timers.go test. The log says: "fail: ticker should have stopped!" and "ticker was stopped (didn't send anything after 750ms)", indicating that the test expected the ticker to stop, but it did not behave as intended.

I was hitting this error in CI, so I asked Copilot to fix it and the fix looks good to me. At least the tests now pass.

[aykevl]

This is a race condition. So it's not surprising it passes now, since the test passes most of the time.

Can you please explain why this is a correct fix (without using Copilot)?

[cataggar]

@aykevl , unfortunately no. My Go skills aren't good enough to validate Copilot's reasoning:

// Set period to 0 to prevent the timer from being re-added to the queue
// if the callback is currently running. This must be done before removing
// the timer to avoid a race condition where the callback re-adds the timer
// after it's been removed.

If it does not make sense, please close. I just used some tokens trying to help out.