Track progress of any POST request

https://stackoverflow.com/questions/19126994/what-is-the-cleanest-way-to-get-the-progress-of-jquery-ajax-request

It seems possible to track progress for any POST request but superagent by documentation doesn't support that. I tried to attach progress event for POST request and it worked incorrect: during upload I received 2 events, both had `percent: 100`.

I'm sending application/json body.