```go
package main
import (
"fmt"
"github.com/moovweb/gokogiri"
"github.com/moovweb/gokogiri/xpath"
"io/ioutil"
)
func main() {
xml, _ := ioutil.ReadFile("elrc-20130531.xml")
doc, _ := gokogiri.ParseXml(xml)
defer doc.Free()
xp := doc.DocXPathCtx()
xp.RegisterNamespace("xbrli", "http://www.xbrl.org/2003/instance")
x := xpath.Compile("//xbrli:context")
groups, err := doc.Search(x)
if err != nil {
fmt.Println(err)
}
for i, group := range groups {
fmt.Println(i, group.Content())
}
}
```
```
go get
go run main.go
```