Show HTTP server error, bumped to v4

main.go

@@ -17,7 +17,7 @@ import (
 	"strings"
 )
 
-const VERSION = "v3"
+const VERSION = "v4"
 
 var (
 	flagVerbose       bool
@@ -49,7 +49,11 @@ func main() {
 	http.HandleFunc("/sites", actionSites)
 
 	log.Println("Listen on [::]:5123")
-	http.ListenAndServe("[::]:5123", nil)
+	err := http.ListenAndServe("[::]:5123", nil)
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
 }
 
 func replaceTilde(str string) string { // {{{