binance_cfutures: TimeOnForce is an optional order submission field (#867)

Do not add it to the request unless filled out as the API will deny the
request otherwise.

exchanges/binance/binance_cfutures.go

@@ -1000,7 +1000,9 @@ func (b *Binance) FuturesNewOrder(ctx context.Context, x *FuturesNewOrderRequest
 		params.Set("positionSide", x.PositionSide)
 	}
 	params.Set("type", x.OrderType)
-	params.Set("timeInForce", x.TimeInForce)
+	if string(x.TimeInForce) != "" {
+		params.Set("timeInForce", string(x.TimeInForce))
+	}
 	if x.ReduceOnly {
 		params.Set("reduceOnly", "true")
 	}

exchanges/binance/binance_test.go

@@ -923,7 +923,7 @@ func TestFuturesNewOrder(t *testing.T) {
 			Symbol:      currency.NewPairWithDelimiter("BTCUSD", "PERP", "_"),
 			Side:        "BUY",
 			OrderType:   "LIMIT",
-			TimeInForce: "GTC",
+			TimeInForce: BinanceRequestParamsTimeGTC,
 			Quantity:    1,
 			Price:       1,
 		},

exchanges/binance/binance_wrapper.go

@@ -956,10 +956,15 @@ func (b *Binance) SubmitOrder(ctx context.Context, s *order.Submit) (order.Submi
 			return submitOrderResponse, fmt.Errorf("invalid side")
 		}
 
-		var oType string
+		var (
+			oType       string
+			timeInForce RequestParamsTimeForceType
+		)
+
 		switch s.Type {
 		case order.Limit:
 			oType = cfuturesLimit
+			timeInForce = BinanceRequestParamsTimeGTC
 		case order.Market:
 			oType = cfuturesMarket
 		case order.Stop:
@@ -975,13 +980,14 @@ func (b *Binance) SubmitOrder(ctx context.Context, s *order.Submit) (order.Submi
 		default:
 			return submitOrderResponse, errors.New("invalid type, check api docs for updates")
 		}
+
 		o, err := b.FuturesNewOrder(
 			ctx,
 			&FuturesNewOrderRequest{
 				Symbol:           s.Pair,
 				Side:             reqSide,
 				OrderType:        oType,
-				TimeInForce:      "GTC",
+				TimeInForce:      timeInForce,
 				NewClientOrderID: s.ClientOrderID,
 				Quantity:         s.Amount,
 				Price:            s.Price,

exchanges/binance/cfutures_types.go

@@ -212,7 +212,7 @@ type FuturesNewOrderRequest struct {
 	Side             string
 	PositionSide     string
 	OrderType        string
-	TimeInForce      string
+	TimeInForce      RequestParamsTimeForceType
 	NewClientOrderID string
 	ClosePosition    string
 	WorkingType      string