add get http.Client interface

[zhangyongding]

Connection adds a new Client () interface for customizing http.Client

[otoolep]

While the goal makes sense, this doesn't seem like idiomatic Go. It would be better if this library was modified to take a HTTP client object, instead of creating one on the fly.

I realize that would be a lot more work however.

[zhangyongding]

Can you check the new pr？

[otoolep]

Thanks.

The fundamental issue here however is that the Go code in this library is not in great shape. It doesn't use proper Go patterns, so this change is kinda making it worse (though I understand why).

This library needs a rewrite, but one that doesn't change the API. For example it needs proper NewConnection calls, for example, into which one would pass a HTTP client.

[otoolep]

@zhangyongding -- is there something specific you want to control? That you can't do today?

[zhangyongding]

I hope to open up the rqliteApiCall interface and the parameter settings in the assemblleURL interface