There seems to be some confusion about generating a ShadowJar's manifest file when using Kotlin DSL, so this simple application shows how I am doing it. If my method is not the idiomatic way to accomplish this task, please post your suggestions.
SimpleShdaow is a Kotlin application that properly builds a ShadowJar (aka, "fat-jar, uber-jar") using Gradle and Kotlin DSL.
The following command will launch the ShadowJar and write "Howdy!" on the terminal:
java -jar simpleshadow-1.0.0-all.jar