Maven BuildNumber plugin problem

[FrancescoMez79]

Dear Support,
we have a Jhipster application that use this application version in pom.xml:
0.0.2-SNAPSHOT

We want to add the buildnumber to our application version.
We have found the plugin Build-number:
https://www.mojohaus.org/buildnumber-maven-plugin/usage.html

We have added in pom.xml under pluginManagement section the plugin "buildnumber-maven-plugin"
..



org.codehaus.mojo
buildnumber-maven-plugin
3.0.0


validate

create




true
true


..

and added the field "finalName" with -${buildNumber}:
..

${project.artifactId}-${project.version}-${buildNumber}
..

After run the build command :
./mvnw clean install

in target we see that the buildnumber is setted to null:
myapp-0.0.2-SNAPSHOT-null.jar

Can you please help me to understand the problem?

Thanks,
Francesco