import { Deno } from "https://deno.land/x/deno@v1.41.0/cli/tsc/dts/lib.deno.unstable.d.ts";
const { UnsafeCallback } = Deno;
Decrements the callback's reference counting and returns the new reference count.
Calling unref() does not stop a callback from waking up the Deno
event loop when called from foreign threads.
If the callback's reference counter is zero, it no longer keeps Deno's process from exiting.