GO Lang Unable to get XML header in response

I have a xml stored in db which i am unmarshalling using xml.unmarshall in GO with the struct I defined. When getting the API response I am not getting the XML header and also the namespace.

type Entity struct {
    XMLName    xml.Name `xml:"entity" json:"-"`
etc..
    }

while sending response

func get(c *gin.Context) {

...

entity=new(model.Entity)
offeredContentTypes := []string{"application/xml", "application/json"}
    c.Negotiate(http.StatusOK, gin.Negotiate{
        Offered:  offeredContentTypes,
        XMLData:  entity,
        JSONData: entity,
    })
}

the xml entity I have in db has the required header as well as namespace

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><entity xmlns:ns2="http://abc/xyz">....</entity>

this is the type of response I get

<entity>...</entity>

How can I fix this so that i get both xml header as well as namespace??