[付款] pay.go 增加 GetTransfer 方法 (#400)

pay/pay.go

@@ -5,6 +5,7 @@ import (
 	"github.com/silenceper/wechat/v2/pay/notify"
 	"github.com/silenceper/wechat/v2/pay/order"
 	"github.com/silenceper/wechat/v2/pay/refund"
+	"github.com/silenceper/wechat/v2/pay/transfer"
 )
 
 //Pay 微信支付相关API
@@ -31,3 +32,8 @@ func (pay *Pay) GetNotify() *notify.Notify {
 func (pay *Pay) GetRefund() *refund.Refund {
 	return refund.NewRefund(pay.cfg)
 }
+
+// GetTransfer 付款
+func (pay *Pay) GetTransfer() *transfer.Transfer {
+	return transfer.NewTransfer(pay.cfg)
+}