managing number of threads creation in websocket API

[StrikeCPP]

At present when we create a web_socket client of type websocket_callback_client then automatically a lot of threads are created by default for handling different actions of connection. In my case its close to 20 threads which are created by default. I'm using linux OS to run my program.

libboost: 1.75 openssl: 1.1.0 kernel version: 4.19.57 g++ : gcc version 9.3.0 (Gentoo 9.3.0 p2)

I would like to know that how can I control the number threads being created per web sockets client creation. I tried searching all the implementation of the program in cpprestsdk but could not find anything related to thread being used by web sockets API.

Any help will deeply appreciated.