GET requests generally cannot accept a body (nor a Content-Length); this is a restriction of the underlying HTTP protocol, not a Salesforce limitation.
This is called out in RFC 7231, 4.3.1:
A payload within a GET request message has no defined semantics; sending a payload body on a GET request might cause some existing implementations to reject the request.
Also, the Salesforce REST API documentation doesn't even mention that a 411 error code is possible.
Taking a look at the standard HTTP status codes, 411 is described as
411 Length Required. I feel like that might be a bug, as a Content-Length has been provided, but would be unacceptable as a response in this scenario. In theory, the 400 status code should be more appropriate here, as you're violating expectations of the underlying protocol.
Your request should look like:
Authorization: Bearer 00D...
There should be no Content-Length, and there should be no body. If you intend to send data to the server, you should use PATCH, PUT, or POST. OPTIONS, GET, and DELETE are not specified as accepting a body/payload, and no such body should be supplied.