fix: avoid data race when watching request cancellation

sdk/api/handlers/handlers.go

@@ -339,12 +339,13 @@ func (h *BaseAPIHandler) GetContextWithCancel(handler interfaces.APIHandler, c *
 		}
 	}
 	newCtx, cancel := context.WithCancel(parentCtx)
+	cancelCtx := newCtx
 	if requestCtx != nil && requestCtx != parentCtx {
 		go func() {
 			select {
 			case <-requestCtx.Done():
 				cancel()
-			case <-newCtx.Done():
+			case <-cancelCtx.Done():
 			}
 		}()
 	}