fix: improve connection closing (#156)

Author: gssbzn

mongodbatlas/mongodbatlas.go

@@ -391,9 +391,18 @@ func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*Res
 	}
 
 	defer func() {
-		if rerr := resp.Body.Close(); err == nil {
-			err = rerr
+		// Ensure the response body is fully read and closed
+		// before we reconnect, so that we reuse the same TCP connection.
+		// Close the previous response's body. But read at least some of
+		// the body so if it's small the underlying TCP connection will be
+		// re-used. No need to check for errors: if it fails, the Transport
+		// won't reuse it anyway.
+		const maxBodySlurpSize = 2 << 10
+		if resp.ContentLength == -1 || resp.ContentLength <= maxBodySlurpSize {
+			_, _ = io.CopyN(ioutil.Discard, resp.Body, maxBodySlurpSize)
 		}
+
+		resp.Body.Close()
 	}()
 
 	response := &Response{Response: resp}