Upgrade to Kotlin 1.2.21

build.gradle

@@ -14,7 +14,7 @@ buildscript {
 plugins {
 	id "com.gradle.build-scan" version "1.8"
 	id "io.spring.dependency-management" version "1.0.3.RELEASE" apply false
-	id "org.jetbrains.kotlin.jvm" version "1.2.20" apply false
+	id "org.jetbrains.kotlin.jvm" version "1.2.21" apply false
 	id "org.jetbrains.dokka" version "0.9.15"
 	id "org.asciidoctor.convert" version "1.5.6"
 }
@@ -50,7 +50,7 @@ configure(allprojects) { project ->
 	ext.junitJupiterVersion  = "5.0.3"
 	ext.junitPlatformVersion = "1.0.3"
 	ext.junitVintageVersion  = "4.12.3"
-	ext.kotlinVersion        = "1.2.20"
+	ext.kotlinVersion        = "1.2.21"
 	ext.log4jVersion         = "2.10.0"
 	ext.nettyVersion         = "4.1.20.Final"
 	ext.reactorVersion       = "Bismuth-SR5"