将innerxml解组为字符串指针

Should I be able to define a struct that contains a *string and uses this to unmarshal innerxml content.

See here for an example https://play.golang.org/p/oaGu0rKYNgi

I expect the Struct variable, Containment, to point to

<top xmlns="http://example.com/schema/1.2/config"/>

Instead it is nil.

I see similar example structs in src/encoding/xml/marshal_test.go

type IndirInnerXML struct {
    T1       T1
    InnerXML *string `xml:",innerxml"`
    T2       T2
}

Any help much appreciated.

The test you quoted is for Marshal, not for Unmarshal. There is no test for *string for innerxml for Unmarshal; there is one to prove that it won't work with []string, and that it will work with []byte and string, but that's it. According to the docs for Unmarshal:

If the struct has a field of type []byte or string with tag ",innerxml", Unmarshal accumulates the raw XML nested inside the element in that field. The rest of the rules still apply.

It supports []byte and string exclusively for unmarshalling inner XML. Whether *string should be supported is a question for the Go maintainers.