fix: fmt issue with struct

Fix issue swaggo#1150

To summarize of the issue, running `swag fmt` will set (at least) 2 spaces between the attribute tag and the rest of the comment.

For instance:

```
type Example struct {
	Foobar string
} // @name  Example
```

However the doc generation doesn't interpret this correctly for struct (it completly ignore it).

So there are 2 solutions:

- fix the indent (which is feel more natural)
- fix the doc generation to correctly parse 2 spaces

This commit is fixing the indent part.

Basically I just set the padding=1 on `tabwriter`.

The cons is that it will also impacts all other godocs.

For instance (taken from the readme):

```
// @title          Swagger Example API
// @Version        1.0
// @description    This is a sample server celler server.
// @termsofservice http://swagger.io/terms/
```

formatter.go

@@ -78,7 +78,7 @@ func formatComments(fileName string, contents []byte, formattedComments []byte,
 }
 
 func formatFuncDoc(commentList []*ast.Comment, formattedComments io.Writer, oldCommentsMap map[string]string) {
-	w := tabwriter.NewWriter(formattedComments, 0, 0, 2, ' ', 0)
+	w := tabwriter.NewWriter(formattedComments, 0, 0, 1, ' ', 0)
 
 	for _, comment := range commentList {
 		text := comment.Text