Clarify that `mvn package` needs to be run first.
@@ -20,6 +20,10 @@ The samples have files to support both Maven and Gradle. To use the IDE plugins
[Using Maven and the App Engine Plugin](https://cloud.google.com/appengine/docs/flexible/java/using-maven)
& [Maven Plugin Goals and Parameters](https://cloud.google.com/appengine/docs/flexible/java/maven-reference)
+### Building
+
+ $ mvn package
+
### Running locally
$ mvn cargo:run
