func NewResolver(serviceName string) *EtcdResolver {
	return &EtcdResolver{ServiceName: serviceName}
}
NewResolver return EtcdResolver with service name
package etcd
import (
	"errors"
	"fmt"
	etcd "github.com/coreos/etcd/clientv3"
	"github.com/golang/glog"
	"google.golang.org/grpc/naming"
	"strings"
	"time"
)
type EtcdResolver struct {
	ServiceName string  
}