fix issue in batch number for package gdb

.example/database/gdb/mysql/gdb_batch_insert.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+	"github.com/gogf/gf/frame/g"
+)
+
+func main() {
+	db := g.DB()
+	db.SetDebug(true)
+	list := make(g.List, 0)
+	for i := 0; i < 100; i++ {
+		list = append(list, g.Map{
+			"name": fmt.Sprintf(`name_%d`, i),
+		})
+	}
+	r, e := db.Table("user").Data(list).Batch(2).Insert()
+	if e != nil {
+		panic(e)
+	}
+	if r != nil {
+		fmt.Println(r.LastInsertId())
+	}
+}