How does Web server handle locking ( await and signal) of request between API calls?

We're tasked to implement REST APIs: 1 for holding a request, 1 for releasing the request, and the rest for the in-between processing.

Given that these API calls are on a web server and these are called on separate request, can the signal() match which request is on-hold( await state)?

Please help! There's something I'm not getting here. Thanks in advance!

hold(){ 
    hold.await();
}

inBetween(){
    // do some processing
}

release(){
    hold.signal();
}