session.alpnProtocol

• 类型：<string> | <null>

协商后的 ALPN 协议。这是在处理客户端 hello 之前的 null。一旦 ALPN 协商完成，这就是协议字符串。在 QUIC 中 ALPN 是强制的，所以在成功连接中它从不为 false，不像 node:tls 那样是可选的。

🌐 The negotiated ALPN protocol. This is null before the client hello is processed. Once ALPN has been negotiated, this is the protocol string. ALPN is mandatory in QUIC so this is never false on successful connections, unlike node:tls where this is optional.