func NewDecoder(reader io.Reader) *Decoder {
	return NewDecoderWithPrefix(reader, attrPrefix, textPrefix)
}
NewDecoder create new decoder instance
package xml2map
import (
	"encoding/xml"
	"errors"
	"io"
	"strings"
)
const (
	attrPrefix = "@"
	textPrefix = "#text"
)
var (
	ErrInvalidDocument = errors.New("invalid document")
	ErrInvalidRoot = errors.New("data at the root level is invalid")
)
type node struct {
	Parent  *node
	Value   map[string]interface{}
	Attrs   []xml.Attr
	Label   string
	Text    string
	HasMany bool
}
type Decoder struct {
	r          io.Reader
	attrPrefix string
	textPrefix string
}