Add expression functions with context boundaries

README.md

@@ -304,6 +304,19 @@ Use `coroutineContext()` only at Go interop boundaries that require a
 `context.Context`; it returns the ambient scope context without exposing it in
 the Gotlin function signature.
 
+HTTP handlers can establish a request-scoped ambient context with an
+expression-bodied function:
+
+```kotlin
+fun handle(request: *http.Request) = withContext(request.context()) {
+    service.processRequest()
+}
+```
+
+`withContext` is a structured boundary. It waits for children, propagates
+failures, and, when nested, combines cancellation from the parent coroutine and
+the supplied Go context.
+
 For conventional Go APIs whose first parameter is `context.Context`, Gotlin
 normally injects that ambient context automatically when the argument is
 omitted: