You can do it in two ways. Firstly, you can make comment a part of a larger struct that embeds members and make it marshal a comment every time a member is marshalled:
type Members struct {
XMLName xml.Name `xml:"members"`
Members []CommentedMember
}
type CommentedMember struct {
Member
comment xml.Comment
}
func (cm CommentedMember) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
if cm.comment != nil {
err := e.EncodeToken(cm.comment)
if err != nil {
return err
}
}
return e.Encode(cm.Member)
}
type Member struct {
XMLName xml.Name `xml:"member"`
}
The second way is to create a separate Comment
type and make your Members
struct contain different types:
type Members2 struct {
XMLName xml.Name `xml:"members"`
Members []interface{}
}
type Comment string
func (cm Comment) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
if cm != "" {
return e.EncodeToken(xml.Comment(cm))
}
return nil
}
type Member struct {
XMLName xml.Name `xml:"member"`
}
Here are both on the playground: https://play.golang.org/p/3n-xH1Zc-n.