Gradlew runnable jar file

I am trying to create a runnable jar file for my project. I have instrumented cobertura and when I run “gradlew installDist” the jar file is created. However, when I run the jar file it gives “no main manifest attribute, in build/install/Web/lib/myJar.jar” error.

I have included manifest in my build.gradle file with the main class.
manifest {
attributes ‘Main-Class’: ‘com.peoject.myMainClass’

Can someone tell me what I am doing wring here?

Please provide a project on GitHub that reproduces the issue.