mail/message.go
func (m *Message) AddAttachment(name, contentType string, r io.Reader) error {
	m.Attachments = append(m.Attachments, Attachment{
		Name:        name,
		ContentType: contentType,
		Reader:      r,
		Embedded:    false,
	})

	return nil
}
func (m *Message) AddAttachment(name, contentType string, r io.Reader) error {
	m.Attachments = append(m.Attachments, Attachment{
		Name:        name,
		ContentType: contentType,
		Reader:      r,
		Embedded:    false,
	})

	return nil
}
//AddAttachment adds the attachment to the list of attachments the Message has.