WebSocket from dart:io forces all headers to lowercase

[CoocooFroggy]

When trying to connect with WebSocket.connect(), headers are changed to lowercase. For example, see the below code:

final channel = await WebSocket.connect(
  'wss://example.com/?v=2',
  headers: {'Origin': 'https://example.com'},
);

channel.listen((message) {
  print(message);
});

Origin: https://example.com becomes origin: https://example.com

I do not have control of the server and thus cannot fix the back end to be case-insensitive.

Perhaps a solution similar to #33501 could be implemented ({bool preserveHeaderCase: false}).

[CoocooFroggy]

I can try to add this

[CoocooFroggy]

Doing my best trying to contribute 😅
https://dart-review.googlesource.com/c/sdk/+/268062