Fix issue #1529 : DoTimeout timeout failure

[kukayiyi]

As discussed in #1529 , the main problem with the timeout failure is that req.timeout is not passed to dial to pause the dialing in time. One solution is to create a temporary dial. In order not to affect the original dial of HostClient, I choose to add the dialTimeout parameter in the dialHostHard function to control the dialing time. It will fail if HostClient.dial has been set, but general users should not set dial. In fact, I think the most appropriate solution is to make HostClient have a Dialer with a timeout attribute so that timeout can be set separately without affecting other settings and use HostClient.Dialer.dial instead of HostClient.dial, but obviously this will change a lot of code.

[kukayiyi]

I've looked at other code, and when the connection is successfully established, the timeout is affected by readTimeout and writeTimeout as expected, so this change doesn't change the timeout control normally, only when the connection fails. I think the connection establish time should be able to be set, just like python request

[erikdubbelboer]

I agree changing the Dail on HostClient is probably not a good idea as it isn't backwards compatible. If users set their own Dial then they can handle the timeouts in there as well.

I like the change this way. Thanks!