This lib is designed to include ESPAsyncWebSrv, because there just have ESPAsyncWebSrv on Arduino, but some other libs may still use the old one, so they need to to be inluded by this lib.
How to use? Just download my code in .ZIP format, and use the "import .zip lib" function in Arduino.
Async HTTP and WebSocket Server for ESP8266 Arduino
For ESP8266 it requires ESPAsyncTCP To use this library you might need to have the latest git versions of ESP8266 Arduino Core
For ESP32 it requires AsyncTCP to work To use this library you might need to have the latest git versions of ESP32 Arduino Core