diff --git a/go.mod b/go.mod
index bdfebdd..0daa42d 100644
--- a/go.mod
+++ b/go.mod
@@ -12,3 +12,5 @@ require (
 	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
 	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df
 )
+
+go 1.13