Not able to override default values in gatling-default.conf with sbt

Gatling (Open-Source)
1

I have tried to run my scenario for 300 users at once, but after 60 seconds my test has terminated, but the process is running in backend.

I have tried to increase connection timeout property in gatling sbt bundle, i have tried following approach :

 
          System.setProperty("gatling.http.ahc.connectTimeout", "120000")

but still after 60 seconds my test has been failed, but the scenarios are running in backend.

Could someone please help me how to override default Connection Timeout in .sbt bundled jar?

my current gatling version is 2.2.3