private String get(final String override, final Config config, final String path)
      throws MojoExecutionException {
    if (override != null) {
      return override;
    }
    try {
      return expand(config.getString(path));
    } catch (ConfigException.Missing e) {
      return null;
    }
  }
Set the networking mode for the RUN instructions during build
src/main/java/com/spotify/docker/BuildMojo.java