Fix AWS sample to build better with Gradle

spring-cloud-function-samples/function-sample-aws/build.gradle

@@ -1,12 +1,12 @@
 buildscript {
 	ext {
-		springBootVersion = '1.5.12.RELEASE'
-		wrapperVersion = '1.0.11.RELEASE'
+		springBootVersion = '2.0.3.RELEASE'
+		wrapperVersion = '1.0.13.BUILD-SNAPSHOT'
 		shadowVersion = '2.0.1'
 	}
 	repositories {
-		jcenter()
 		mavenLocal()
+		jcenter()
 		mavenCentral()
 		maven { url "https://repo.spring.io/snapshot" }
 		maven { url "https://repo.spring.io/milestone" }
@@ -22,7 +22,8 @@ apply plugin: 'java'
 apply plugin: 'maven'
 apply plugin: 'eclipse'
 apply plugin: 'com.github.johnrengelman.shadow'
-apply plugin: 'spring-boot'
+apply plugin: 'io.spring.dependency-management'
+apply plugin: 'org.springframework.boot'
 apply plugin: 'org.springframework.boot.experimental.thin-launcher'
 
 group = 'io.spring.sample'
@@ -44,11 +45,11 @@ ext {
 }
 ext['reactor.version'] = "3.1.7.RELEASE"
 
-assemble.dependsOn = [shadowJar, bootRepackage]
+assemble.dependsOn = [shadowJar, thinJar]
 
 jar {
   manifest {
-    attributes 'Start-Class': 'example.Config'
+    attributes 'Main-Class': 'example.Config'
   }
 }