intellij IDEA - not found: value atOnceUsers - error -- can not resolve symbol atOnceUsers

Gatling (Open-Source)
#1

Hi,

I created project using the command line -

mvn archetype:generate \
-DarchetypeCatalog=http://repository.excilys.com/content/groups/public/archetype-catalog.xml

Imported project to IDE using File->new->project from existing sources using maven.

I created a simple simulaton script. But while running the Engine, getting following error. 
I make sure that 2.0.0-M3a gatling libraries available in external libraries. 
Do I need to import any extra to resolve this issue?

Error:(23, 19) not found: value atOnceUsers
	setUp(scn.inject(atOnceUsers(1000))).protocols(httpProtocol)

Thanks,
Rag