code: func NewGetHeadersCmd(blockLocators []string, hashStop string) *GetHeadersCmd {
  	return &GetHeadersCmd{
  		BlockLocators: blockLocators,
  		HashStop:      hashStop,
  	}
  }
docs: // NewGetHeadersCmd returns a new instance which can be used to issue a
  // getheaders JSON-RPC command.
  //
  // NOTE: This is a btcsuite extension ported from
  // github.com/decred/dcrd/dcrjson.