protobuf解组未知消息

Question

I have a listener which receives protobuf messages. However it doesn't know which type of message comes in when. So I tried to unmarshal into an interface{} so I can later type cast:

var data interface{}
err := proto.Unmarshal(message, data)
if err != nil {
  log.Fatal("unmarshaling error: ", err)
}
log.Printf("%v
", data)

However this code doesn't compile:

cannot use data (type interface {}) as type proto.Message in argument to proto.Unmarshal:
  interface {} does not implement proto.Message (missing ProtoMessage method)

How can I unmarshal and later type cast an "unknown" protobuf message in go?