Unknown desc = Please retry again, server is not ready to accept requests exit status 1

Hi
I try to use Dgraph with Go but when run the program show this error :

2019/09/11 11:36:52 rpc error: code = Unknown desc = Please retry again, server is not ready to accept requests
exit status 1

package main

import (
	"context"
	"fmt"
	"log"

	dgo "github.com/dgraph-io/dgo/v2"
	"github.com/dgraph-io/dgo/v2/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("192.168.0.11:31908", grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dgraphClient := dgo.NewDgraphClient(api.NewDgraphClient(conn))
	ctx := context.Background()

	txn := dgraphClient.NewTxn()
	defer txn.Discard(ctx)
}

dgraph version is 1.1,0
and dgo version is v2

Can you help me?!

Sometimes I have this issue with go, I just use “localhost:9080” instead.