Function rename 

pub async fn rename<P, Q>(src: P, dst: Q) -> Result<()>
where
    P: AsRef<Path>,
    Q: AsRef<Path>,

Renames the file or directory at src to dst, replacing what is at dst if the platform allows it.

Runs std::fs::rename on the thread that polls the future.

Errors

Fails, for example, if src and dst are on different filesystems.