fix error

announcement.gemspec

@@ -264,7 +264,7 @@ if bundle_update_flag
             v["options"].delete "pool_size"
           end
           if !v["options"].nil? && v["options"]["read"].class == String
-            v["options"]["read"] = {mode: v["options"]["read"]}
+            v["options"]["read"] = {"mode"=> v["options"]["read"]}
           end
         end
       end