confuse me about the http::client::options().timeout

[IceCream01]

In the http::client::options().timeout,the timeout is an overall timeout for HTTP requests.

1.the timeout is in seconds,if I want timeout in milliseconds，how to do？
2.I can only bind timeout to http::client, why not bind timeout to request?
3.how to set DNS resolve timeout, connection timeout and read/write timeout?