allprojects {
    repositories {
       ...
       ...
        maven {
            credentials {
                username 'xxxx'
                password 'xxxx'
            }
            url "https://xxxxx-xxxxx-maven.appspot.com"
        }
    }
}

compile'xxx.xxxx.xxxx:example:1.0'
OR
implementation 'xxx.xxxx.xxxx:example:1.0'