Function wait_with_timeout 

pub async fn wait_with_timeout(
    child: &mut Child,
    timeout: Duration,
) -> Result<Option<Output>>

Wait for a child, reading both pipes concurrently so a chatty command cannot deadlock by filling a pipe buffer, and killing it if the deadline passes.

wait_with_output consumes the Child, which is why the timeout path there leaks a live process: there is nothing left to kill. Borrowing instead keeps the handle available.