change server address from string to a type

weed/command/download.go

@@ -2,6 +2,7 @@ package command
 
 import (
 	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/pb"
 	"github.com/chrislusf/seaweedfs/weed/security"
 	"google.golang.org/grpc"
 	"io"
@@ -49,7 +50,7 @@ func runDownload(cmd *Command, args []string) bool {
 	grpcDialOption := security.LoadClientTLS(util.GetViper(), "grpc.client")
 
 	for _, fid := range args {
-		if e := downloadToFile(func() string { return *d.server }, grpcDialOption, fid, util.ResolvePath(*d.dir)); e != nil {
+		if e := downloadToFile(func() pb.ServerAddress { return pb.ServerAddress(*d.server) }, grpcDialOption, fid, util.ResolvePath(*d.dir)); e != nil {
 			fmt.Println("Download Error: ", fid, e)
 		}
 	}