[go-nuts] Multiple Struct switch?

Let's say I have an application that receives json data in two different
formats.

     f1 = `{"pointtype":"type1", "data":{"col1":"val1", "col2":"val2"}}`
     f2 = `{"pointtype":"type2", "data":{"col3":"val3", "col3":"val3"}}`

And I have a struct associated to each type:

     type F1 struct {
       col1 string
       col2 string
     }

     type F2 struct {
       col3 string
       col4 string
     }

Assuming that I use the `encoding/json` library to turn the raw json data
into the struct:
     type Point {
       pointtype string
       data json.RawMessage
     }

How can I decode the data into the appropiate struct just by knowing the
pointtype?

I was trying something along the lines of :

     func getType(pointType string) interface{} {
     switch pointType {
     case "f1":
     var p F1
     return &p
     case "f2":
     var p F2
     return &p
     }
     return nil
     }

Which is not working because the returned value is an interface, not the
proper struct type.
How can I make this kind of switch struct selection work?

[here is a non working example](http://play.golang.org/p/mjNeWlAw6j)