protocol property
The network protocol used with the request, such as "http/1.1", "spdy/3", "h2", "h2c", "webrtc", "tcp", "udp", "quic".
See https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids for details.
Implementation
core.String? protocol;