Generate a fat jar by Gradle Kotlin DSL.

build.gradle.kts

// run gradle jar in the command line to get the jar
plugins {
    java
    application
    kotlin("jvm") version "1.3.60"
}

repositories {
    mavenCentral()
}

dependencies {
    implementation(kotlin("stdlib", "1.3.60")) // 
}

application {
    mainClassName = "package.name.MainClassName" // Don't append Kt to class name.
}

val jar by tasks.getting(Jar::class) {
    manifest {
        attributes["Main-Class"] = application.mainClassName
    }

    from(configurations.compileClasspath.get().map { if (it.isDirectory) it else zipTree(it) })
}