ndjson -> json array (technically golang will take '\n' as a json sep where ndjson is '\r\n' but /shrug)

NDjsonTojsonArr.go

// NDjsonTojsonArr converts newline-delimited json (indented or minified) 
// to a json array. Caller should handle cleanup on error.
func NDjsonTojsonArr(r io.Reader, w io.WriteCloser) error {
	w.Write([]byte("["))

	var m json.RawMessage
	dec := json.NewDecoder(r)
	err := dec.Decode(&m)
	for {
		if _, err = w.Write(m); err != nil {
			return err
		}
		
		if err = dec.Decode(&m); err != nil {
			if err != io.EOF {
				return err
			}
			break
		}
		
		if _, err = w.Write([]byte(",")); err != nil {
			return err
		}
	}
	_, err = w.Write([]byte("]"))
	return err
}