golang rpc not returning when struct has a nested struct

UPDATE

moving from gob encoding to json fixed the issue. However I would still like to know why this was failing to work with gob.

so my client code looks like this

account := new(database.Account)
err := client.Call("AccountDb.FindAccount", "username", account)
if err != nil {
	logger.FATAL.Print(err.Error())
	return
}
logger.INFO.Print(account)

On the server side AccountDb.FindAccount looks like this

func (t *AccountDb) FindAccount(args *string, reply *Account) error {
	reply.Username = "this is a test"
	return nil
}

The struct for Account looks like this

type Account struct {
	Id           int
	Username     string
	Password     string
	Email        string
	Created      time.Time
	LastLoggedIn time.Time
	AccessLevel  int
	Banned struct {
		reason  string
		expires time.Time
	}
}

if I attempt to perform the rpc the requests starts and the server executes the procedure. However the program then hangs and the procedure does not return! If however I remove the Banned anonymous struct from the Account struct it works fine! Why is this? is there a solution to this problem?

edit
the client and server register code looks like this

Client

client, err = rpc.DialHTTP("tcp", "127.0.0.1:9001")
if err != nil {
	logger.FATAL.Panic(err.Error())
}

Server

defer db.Close()
account := new(database.AccountDb)
account.Database = db
rpc.Register(account)
rpc.HandleHTTP()
l, e := net.Listen("tcp", ":9001")
if e != nil {
	logger.FATAL.Fatal("listen error:", e)
}
http.Serve(l, nil)

Evidently, the gob encoder fails to marshal the RPC response because the Banned struct has no exported fields. This playground example exhibits the error:

encode error: gob: type struct { reason string; expires time.Time } 
has no exported fields

If you export the reason/expires fields by capitalizing them, the gob round-trip works OK (see http://play.golang.org/p/YrYFsk6trQ).

The JSON encoder also requires that serialized fields are exported, but it does not return an error if a struct has none. The decode just returns default/zero values. Run http://play.golang.org/p/OBBkB4tPcZ and note that the Banned information is lost on the round-trip.

If you need to detect these kinds of errors in the rpc package, there are two options:

1. Edit rpc/debug.go, set the logDebug flag to true, and rebuild the rpc package, or
2. Implement a ServerCodec that wraps the existing implementation and logs any errors returned by ReadRequestBody/WriteResponse.