feat: Replace mongo package with monc & mon (#2002)

* Replace mongo package with monc & mon

* Add terminal whitespace

* format code

tools/goctl/model/mongo/template/error.tpl

@@ -1,6 +1,12 @@
 package model
 
-import "errors"
+import (
+	"errors"
 
-var ErrNotFound = errors.New("not found")
-var ErrInvalidObjectId = errors.New("invalid objectId")
+	"github.com/zeromicro/go-zero/core/stores/mon"
+)
+
+var (
+	ErrNotFound        = mon.ErrNotFound
+	ErrInvalidObjectId = errors.New("invalid objectId")
+)