How to limit task number in rust future or tokio

just like https://blog.danskingdom.com/limit-the-number-of-c-tasks-that-run-in-parallel/ said, i write a client requests to server by reqwest, but i donot want wast lots of bandwith and/or doss the server. so how to contral the task number in rust future or tokio or reqwest?

I wrote this a long time ago: gist which performs up to ten requests at a time.