How to transfer call?

[pavanputhra]

I am trying to transfer already established call with following code

referReq := sip.NewRequest(sip.REFER, dlg.InviteRequest.Recipient)
inviteCSeq := dlg.InviteRequest.CSeq()
referCSeq := inviteCSeq.SeqNo + 1
cSeqHeader := sip.NewHeader("CSeq", fmt.Sprintf("%d REFER", referCSeq))
referReq.AppendHeader(cSeqHeader)
// Copy necessary headers from the INVITE request
referReq.AppendHeader(dlg.InviteRequest.Via())
referReq.AppendHeader(dlg.InviteRequest.CallID())
referReq.AppendHeader(dlg.InviteRequest.From())
referReq.AppendHeader(dlg.InviteRequest.To())
referReq.AppendHeader(dlg.InviteRequest.Contact())
referReq.AppendHeader(sip.NewHeader("Refer-To", "sip:[email protected]"))
err := dlg.WriteRequest(referReq)

Above refer request is sending message to the address at dlg.InviteRequest.Recipient. What I want instead is to send the refer request to either dlg.InviteRequest.Contact() or via dlg.InviteRequest.Via()

I assumed the set destination would do it and tried the following code.

// contact address is 52.201.213.20:5070
referReq.SetDestination(fmt.Sprintf("%s:%d", dlg.InviteRequest.Contact().Address.Host, dlg.InviteRequest.Contact().Address.Port))

This produced following error

Fail to send ref request error="listen udp 52.201.213.20:5070: bind: cannot assign requested address"

Please help me by showing correct way to transfer the already established call.