Example of root build.gradle file in Groovy

build.gradle

buildscript {
    ext.kotlin_version = '1.2.30'

    ext.compileSdkVersion = 27
    ext.buidToolsVersion = '27.0.2'
    ext.minSdkVersion = 21
    ext.targetSdkVersion = 27

    ext.playVersion = '27.0.2'
    ext.playServicesVersion = '11.8.0'
    ext.firebaseVersion = '11.8.0'
    ext.exoPlayerVersion = '2.6.1'

    ext.daggerVersion = "2.13"
    ext.retrofitVersion = '2.3.0'

    ext.leakCanaryVersion = '1.5.4'
    ext.timberVersion = '4.6.0'

    ext.rxAndroidVersion = '1.2.1'
    ext.rxJavaVersion = '1.3.0'
    ext.rxJava2Version = '2.1.9'
    ext.rxAndroid2Version = '2.0.2'
    ext.rxKotlinVersion = '2.0.0-RC1'

    repositories {
        jcenter()
        mavenCentral()
        maven { url 'https://maven.fabric.io/public' }
        google()
        maven { url 'https://dl.bintray.com/kotlin/kotlin-eap' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.1'
        classpath 'com.google.gms:google-services:3.2.0'
        classpath 'com.google.firebase:firebase-plugins:1.1.5'

        classpath 'com.stanfy.spoon:spoon-gradle-plugin:1.2.2'
        classpath 'io.fabric.tools:gradle:1.24.5'
        classpath 'com.github.triplet.gradle:play-publisher:1.2.0'

        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.21"
        classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlin_version"
    }
}