<project>
  ...
  <build>
    <!-- To define the plugin version in your parent POM -->
    <pluginManagement>
        <plugin>
          <groupId>com.github.gino0631</groupId>
          <artifactId>icns-maven-plugin</artifactId>
          <version>...</version>
        </plugin>
        ...
      </plugins>
    </pluginManagement>
    <!-- To use the plugin goals in your POM or parent POM -->
    <plugins>
      <plugin>
        <groupId>com.github.gino0631</groupId>
        <artifactId>icns-maven-plugin</artifactId>
        <executions>
          <execution>
            <id>create-macosx-icons</id>
            <phase>generate-resources</phase>
            <goals><goal>icns</goal></goals>
            <configuration>
              <outputFile>${project.build.directory}/product/macosx-x64/Applications/${product.name}.app/Contents/Resources/Main.icns</outputFile>
              <icons>
                <icon>icons/main_window_128.png</icon>
              </icons>
            </configuration>
          </execution>
        </executions>
      </plugin>
    ...
    </plugins>
    ...
  </build>
  ...
</project>