RiskManager

- refactor GetOrderSize: add symbol string, bid float64

risk_manager.go

@@ -9,5 +9,5 @@ type RiskManager interface {
 	GetPnL() (float64, float64)
 	GetProfitRate() float64
 
-	GetOrderSize() float64
+	GetOrderSize(symbol string, bid float64) float64
 }