How to map an xml sequence of mixed elements to a go struct?

'm trying to load an XML file that contains an unbounded sequence of mixed elements (a choice in a sequence in the XSD) The file looks like that :

<RootNode>
    <ElementB>...</ElementB>
    <ElementA>...</ElementA>
    <ElementA>...</ElementA>
    <ElementC>...</ElementC>
    <ElementB>...</ElementB>
    <ElementA>...</ElementA>
    <ElementB>...</ElementB>
</RootNode>

I use xml.Unmarshal to initialize and fill these structs :

type RootNode struct {
    ElementA []ElementA
    ElementB []ElementB
    ElementC []ElementC
}

type ElementA struct {
}

type ElementB struct {
}

type ElementC struct {
}

I have working exemple here http://ift.tt/1Avrvjy. The problem is that i need to know the index of the elements in the original sequence. And with that description, this info is lost.

Is there a way to to load elements of type ElementA, ElementB or ElementC in the same array ? More generally, what is the best way to map a list of mixed elements to a go struct ?