Lower Go requirement in go.mod

Signed-off-by: beorn7 <beorn@grafana.com>
diff --git a/go.mod b/go.mod
index cef4dd2..c4022f2 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/beorn7/perks
 
-go 1.12
+go 1.11