Header gets normalized when using req.Header.Set

[blluv]

Setting headers via req.Header.Set causes header names to get normalized (e.g. Sec-WebSocket-Key -> Sec-Websocket-Key).
With gorilla/websocket, the same server accepts the connection without issues, but using this library the handshake fails.

After debugging, I found that the server was specifically expecting Sec-WebSocket-Key, while the client sent the normalized name.
Servers should ideally treat headers case-insensitively, but the normalization might be unintentional, so I wanted to report it.

[mafredri]

What server are you referring to? Could you give a code-sample that reproduces the issue? This library uses .Set and .Values which are already case-insensitive.

I don't quite understand your statement about gorilla working, it seems conflicting since the header is normalized but the server expects case-sensitivity? Ah, I misread. But essentially the server you're using is non-compliant. HTTP/1.1 headers are case-insensitive and the RFC also mentions this.

[mafredri]

FWIW, if you need to support the server as-is, you could use a custom http.Client with a transport that transforms the headers.

Ultimately, we'd like to keep the simplicity here and use req.Headers rather than writing the headers manually, although that is an option.