Start of application vendor in petstore fails because of a groovy error

[ghost]

Aloha,

Steps to Reproduce

1. Cloning this repository
2. Running ./gradlew vendors:run

Expected Behaviour:
Gradle will compile without any problems

Actual Behaviour:
Gradle failed to compile the class

Starting a Gradle Daemon, 1 busy Daemon could not be reused, use --status for details

> Task :vendors:compileGroovy
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.codehaus.groovy.vmplugin.v7.Java7$1 (file:/Users/alaska/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy/2.5.1/e9628b90c92dcfc7cfaf2f987a2dd2fdabbb3dd5/groovy-2.5.1.jar) to constructor java.lang.invoke.MethodHandles$Lookup(java.lang.Class,int)
WARNING: Please consider reporting this to the maintainers of org.codehaus.groovy.vmplugin.v7.Java7$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

> Task :vendors:compileGroovy FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':vendors:compileGroovy'.
> BUG! exception in phase 'semantic analysis' in source unit '/Users/username/git/sideprojects/micronaut-examples/petstore/vendors/src/main/groovy/example/vendors/Vendor.groovy' Unsupported class file major version 56

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 13s
3 actionable tasks: 1 executed, 2 up-to-date

Groovy Verision: 2.8.5 JVM: 12 Vendor: Oracle Corporation OS: Mac OS X
MacOS: Mojave

PS: changed the username in the path of the error message