Go version required should be 1.13, example produce log print error (#649)

diff --git a/README.md b/README.md
index 17537eb..73bd982 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,7 @@
 
 ## Requirements
 
-- Go 1.11+
+- Go 1.13+
 
 ## Status
 
@@ -72,8 +72,9 @@
 
 if err != nil {
     fmt.Println("Failed to publish message", err)
+} else {
+    fmt.Println("Published message")
 }
-fmt.Println("Published message")
 ```
 
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