Response body not always fully read

[eitankatznelson]

The http.Do function documentation states that:

// If the returned error is nil, the Response will contain a non-nil
// Body which the user is expected to close. If the Body is not both
// read to EOF and closed, the Client's underlying RoundTripper
// (typically Transport) may not be able to re-use a persistent TCP
// connection to the server for a subsequent "keep-alive" request.

In the report method, if the response code is <300 the client doesn't read the response body causing connections to get closed by servers.

Simple fix would be to add the line:
ioutil.ReadAll(res.Body)
in the condition block.

[defrankland]

I can also confirm that this is an issue. I was seeing an error from this package:

ERROR: sending request - Post "https://api.segment.io/v1/batch": write on closed buffer

Which I resolved by forking this repo and adding io.Copy(ioutil.Discard, resp.Body) to discard the body in the block where the response body is not currently being read.