Read response body for TCP connection reuse (#1576)

Author: itsksaurabh

github/github.go

@@ -554,7 +554,21 @@ func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*Res
 
 		return nil, err
 	}
-	defer resp.Body.Close()
+
+	defer func() {
+		// 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 := newResponse(resp)