code: func (h *ResponseHeader) VisitAll(f func(key, value []byte)) {
  	if len(h.contentLengthBytes) > 0 {
  		f(strContentLength, h.contentLengthBytes)
  	}
  	contentType := h.ContentType()
  	if len(contentType) > 0 {
  		f(strContentType, contentType)
  	}
  	server := h.Server()
  	if len(server) > 0 {
  		f(strServer, server)
  	}
  	if len(h.cookies) > 0 {
  		visitArgs(h.cookies, func(k, v []byte) {
  			f(strSetCookie, v)
  		})
  	}
  	visitArgs(h.h, f)
  	if h.ConnectionClose() {
  		f(strConnection, strClose)
  	}
  }
docs: // VisitAll calls f for each header.
  //
  // f must not retain references to key and/or value after returning.
  // Copy key and/or value contents before returning if you need retaining them.