Unexport CopilotRequestContext body channel in Go

The body channel is internal framework plumbing: the adapter drains it for
HTTP requests and pumps it to CopilotWebSocketHandler.SendRequestMessage for
WebSocket requests. It was exported only because Go exports by capitalisation;
no other SDK surfaces the body channel on the request context. A consumer
reading it directly (e.g. via RequestContextFrom) would race the adapter's
pump goroutine and lose frames. Lowercase it to body to match the other SDKs
and keep it internal to the adapter layer.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

go/copilot_request_handler.go

@@ -57,11 +57,17 @@ type CopilotRequestContext struct {
 	Method    string
 	URL       string
 	Headers   http.Header
-	// Body yields request body frames as they arrive from the runtime. The
-	// channel is closed when the body ends or the request is cancelled. For
-	// WebSocket requests each frame's Binary flag distinguishes a binary frame
-	// from a UTF-8 text frame; for HTTP it is always a body byte chunk.
-	Body <-chan CopilotWebSocketMessage
+	// body yields request body frames as they arrive from the runtime. It is
+	// unexported framework plumbing: the adapter drains it for HTTP requests
+	// and pumps it to [CopilotWebSocketHandler.SendRequestMessage] for
+	// WebSocket requests. Consumers read the HTTP body via the standard
+	// [http.Request] Body in a custom RoundTripper, or receive WebSocket frames
+	// via SendRequestMessage — never from this channel directly (doing so would
+	// race the adapter's pump goroutine and lose frames). The channel is closed
+	// when the body ends or the request is cancelled. For WebSocket requests
+	// each frame's Binary flag distinguishes a binary frame from a UTF-8 text
+	// frame; for HTTP it is always a body byte chunk.
+	body <-chan CopilotWebSocketMessage
 	// Context is cancelled when the runtime cancels this in-flight request.
 	Context context.Context
 }
@@ -181,7 +187,7 @@ func (h *CopilotRequestHandler) handleHTTP(rctx *CopilotRequestContext, sink *re
 }
 
 func buildHTTPRequest(rctx *CopilotRequestContext) (*http.Request, error) {
-	body := drainBody(rctx.Body)
+	body := drainBody(rctx.body)
 	method := strings.ToUpper(rctx.Method)
 	var bodyReader io.Reader
 	if len(body) > 0 && method != http.MethodGet && method != http.MethodHead {
@@ -278,7 +284,7 @@ func (h *CopilotRequestHandler) handleWebSocket(rctx *CopilotRequestContext, sin
 		defer close(clientDone)
 		for {
 			select {
-			case frame, ok := <-rctx.Body:
+			case frame, ok := <-rctx.body:
 				if !ok {
 					return
 				}
@@ -619,7 +625,7 @@ func (a *copilotRequestAdapter) HttpRequestStart(params *rpc.LlmInferenceHTTPReq
 		URL:       params.URL,
 		Headers:   headers,
 		Transport: transport,
-		Body:      bodyCh,
+		body:      bodyCh,
 		Context:   ctx,
 	}
 	sink := &responseSink{requestID: params.RequestID, adapter: a, exchange: exchange}