tokio_util::run and tokio::run_on_current_thread should accept Future<Output=()> instead of Future<Output=Result<(), ()>>. Currently, all the passed futures have to add Ok(()) or futures::future::ok(()) unnecessarily to call this method.

This commit moves HTTP client to lazy_static. Effectively HTTP client is shared by whole Deno process and will reuse connections.

Preventing release v0.26.0
This reverts commit 81efa9d9.