The Extended JSON encoder does not support encoding arrays and slices by themselves. The decoder does support decoding JSON arrays into slices. Add support for encoding arrays and slices to a JSON array.

(original description below)

What is the best way to build a JSON Producer. My first approach was to make this: 

// JSONProducer creates a new JSON producer
JSONProducer() runtime.Producer { 
  return runtime.ProducerFunc(func(writer io.Writer, data interface{})    error { 
    valueWriter, _ := bsonrw.NewBSONValueWriter(writer) enc, _ :=   bson.NewEncoder(valueWriter) 
    return enc.Encode(data)  
  })
}

First this version seems to work. But it leads to two different errors, that I dont understand.
1. runtime error: invalid memory address or nil pointer dereference
2. WriteArray can only write a Array while positioned on a Element or Value but is positioned on a TopLevel