Fix missing usageMetadata in streamed aggregated response (#174) (#175)

Author: jdoucy

.changeset/quick-horses-retire.md

@@ -0,0 +1,5 @@
+---
+"@google/generative-ai": patch
+---
+
+Fix missing usageMetadata in streamed aggregated response (#174)

packages/main/src/requests/stream-reader.ts

@@ -188,6 +188,9 @@ export function aggregateResponses(
         }
       }
     }
+    if (response.usageMetadata) {
+      aggregatedResponse.usageMetadata = response.usageMetadata;
+    }
   }
   return aggregatedResponse;
 }