优化extend.GetBjCodes,直接输出代码

extend/codes-bj.go

@@ -4,6 +4,14 @@ import (
 	"github.com/injoyai/tdx"
 )
 
-func GetBjCodes() ([]*tdx.BjCode, error) {
-	return tdx.GetBjCodes()
+func GetBjCodes() ([]string, error) {
+	cs, err := tdx.GetBjCodes()
+	if err != nil {
+		return nil, err
+	}
+	ls := []string(nil)
+	for _, v := range cs {
+		ls = append(ls, "bj"+v.Code)
+	}
+	return ls, nil
 }