Making sure the maven compiler version is specified.

Author: trishagee

kotlin-samples/pom.xml

@@ -36,6 +36,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
                 <executions>
                     <execution>
                         <id>compile</id>