code: private void addKeepAliveHeaders(HttpHeaders headers) {
          if (protocol == H1 || protocol == H1C) {
              headers.set(HttpHeaderNames.CONNECTION, "keep-alive");
          } else {
              // Do not add the 'connection' header for HTTP/2 responses.
              // See https://tools.ietf.org/html/rfc7540#section-8.1.2.2
          }
      }
docs: Sets the keep alive header as per:
  - https://www.w3.org/Protocols/HTTP/1.1/draft-ietf-http-v11-spec-01.html#Connection