[hyper-1.0][Question] Why `http2::handshake` has an executor parameter, while `http1::handshake` doesn't?

[slinkydeveloper]

Version
Hyper 1.0-rc3

Description
I've started looking into porting my application to hyper 1.0, and I'm currently going through the hyper 1.0 APIs to understand all the various details. One thing got my attention: why http2::handshake gets an executor parameter, while http1::handshake doesn't? I would expect the Connection I get out of handshake to be the only task spawned for the tcp connection, handling the http/2 state, but apparently it's not. Following the code I see that this executor is sometimes invoked for implementing the ping pong, right? Or am I missing something else?

Anyway, thank you so much for Hyper 1.0!