Set http client util default timeout. (#61)

diff --git a/util/rest/client.go b/util/rest/client.go
index c6c8032..0d8c0dd 100644
--- a/util/rest/client.go
+++ b/util/rest/client.go
@@ -91,6 +91,7 @@
 		gzip: gzip,
 		client: &http.Client{
 			Transport: transport,
+			Timeout:   30 * time.Second,
 		},
 	}