download file from github in project building with com.googlecode.maven-download-plugin (Authentication)

I was trying to download some files that are present on github during the project maven building. I tried this solution but it only works with public repo or without authentication. I tried to use username and password authentication but it doesn't work. Anyone have any ideas?

<plugin>
<groupId>com.googlecode.maven-download-plugin</groupId>
<artifactId>download-maven-plugin</artifactId>
<version>1.6.8</version>
<executions>
    <execution>
        <id>${jsonschema.document.name}-execution</id>
        <phase>generate-sources</phase>
        <goals>
            <goal>wget</goal>
        </goals>
        <configuration>
            <uri>${jsonschema.uri}${jsonschema.document.name}</uri>
            <username>...........</username>
            <password>...........</password>
            <outputFileName>${jsonschema.document.name}</outputFileName>
            <outputDirectory>${jsonschema.location}</outputDirectory>
            <skipCache>true</skipCache>
        </configuration>
    </execution>
</executions>