Hello @kartik,
From their source, the method used to return false until it was changed in API 21.
public boolean isUserAGoat() {
    return false;
}
It looks like the method has no real use for us as developers. .
In API 21 the implementation was changed to check if there is an installed app with the package com.coffeestainstudios.goatsimulator
public boolean isUserAGoat() {
    return mContext.getPackageManager()
            .isPackageAvailable("com.coffeestainstudios.goatsimulator");
}
Hope this works!!