Function reap_or_kill 

pub fn reap_or_kill(
    child: &mut Child,
    timeout: Duration,
) -> Result<Option<ExitStatus>>

Wait for an already-spawned child up to timeout, killing and reaping it if it overruns. Returns Ok(Some(status)) if it exited on its own, or Ok(None) if it was killed for exceeding the timeout. Either way the child is reaped, so a fire-and-forget caller can’t leak a zombie or a runaway process.