Add new tests to presubmit, fix errors

ct/go/util/gs.go

Index: ct/go/util/gs.go
diff --git a/ct/go/util/gs.go b/ct/go/util/gs.go
index 0decd4f4455f68b6b21b792fbd34116dc4a7a183..279993c7288cea199d96ea6089831cfb60ab0043 100644
--- a/ct/go/util/gs.go
+++ b/ct/go/util/gs.go
@@ -140,7 +140,7 @@ func (gs *GsUtil) DownloadWorkerArtifacts(dirName, pagesetType string, workerNum
 			fileName := filepath.Base(result.Name)
 
 			wg.Add(1)
-			go func() {
+			go func(result *storage.Object) {
 				defer wg.Done()
 				respBody, err := getRespBody(result, gs.client)
 				if err != nil {
@@ -160,7 +160,7 @@ func (gs *GsUtil) DownloadWorkerArtifacts(dirName, pagesetType string, workerNum
 					return
 				}
 				glog.Infof("Downloaded gs://%s/%s to %s", GS_BUCKET_NAME, result.Name, outputFile)
-			}()
+			}(result)
 		}
 		if len(resp.NextPageToken) > 0 {
 			req.PageToken(resp.NextPageToken)