update docker server config parse

cmd/rootcmd.go

@@ -21,7 +21,7 @@ var (
 )
 
 func init() {
-	RootCmd.PersistentFlags().StringVarP(&rewardAddr, "reward", "r", "0x84A3175be614F5886f99Da506dF08682DF530739", "please enter a reward address")
+	RootCmd.PersistentFlags().StringVarP(&rewardAddr, "reward", "r", "", "please enter a reward address")
 	RootCmd.PersistentFlags().StringVarP(&dockerServer, "docker_server", "d", "", "please enter docker server address")
 	cobra.OnInitialize(initConfig)
 }