update doc

@@ -56,7 +56,7 @@ Processors:
       Hosts:
         - "172.16.141.4:9200"
         - "172.16.141.5:9200"
-      DailyIndexPrefix: k8s_pro-
+      Index: {.event}-2006.01.02
 ```
 
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@@ -16,8 +16,6 @@ import (
 	"github.com/tal-tech/go-zero/core/service"
 )
 
-const dateFormat = "2006.01.02"
-
 var configFile = flag.String("f", "etc/config.yaml", "Specify the config file")
 
 func main() {