http.go
func (resp *Response) SetBodyStreamWriter(sw StreamWriter) {
	sr := NewStreamReader(sw)
	resp.SetBodyStream(sr, -1)
}
func (resp *Response) SetBodyStreamWriter(sw StreamWriter) {
	sr := NewStreamReader(sw)
	resp.SetBodyStream(sr, -1)
}
// SetBodyStreamWriter registers the given sw for populating response body.
//
// This function may be used in the following cases:
//
//     * if response body is too big (more than 10MB).
//     * if response body is streamed from slow external sources.
//     * if response body must be streamed to the client in chunks
//     (aka `http server push` or `chunked transfer-encoding`).
//
// See also SetBodyStream.