Add support for regex filter

[rleungx]

Considering that we may depend on some other repositories, but we don't care too much about those repos. An alternative would be to support regex filter.

[prashantv]

Substring and regex filters seem OK, but it might be better to start with an explicit "IgnorePackage".

Putting more generic skips makes it easier to accidentally ignore real leaks as well, so want to make it more specific to the type of leak being ignored.

[prashantv]

Is the server under control of the test? If so, closing the server will also close any keep-alive connections, and should avoid leaks. If the server is not under control of the test, but the client is, then the CloseIdleConnections methods can be used to close the idle connections:
https://golang.org/pkg/net/http/#Client.CloseIdleConnections
https://golang.org/pkg/net/http/#Transport.CloseIdleConnections

I would highly recommend closing all connections as part of your test cleaning up any created resources, as there definitely can be real leaks missed by ignoring all HTTP read/write goroutines.

[prashantv]

On the server side, closing the server will close idle connections, see documentation:
https://golang.org/pkg/net/http/#Server.Close
https://golang.org/pkg/net/http/#Server.Shutdown

[prashantv]

That code actually has a leak -- it's not closing the response body. The leak is not an idle connection, but an active connection for a request that hasn't completed, because the response body has not been read and closed. Add a resp.Body.Close() and the leak will go away.