Exec a shell command in Go

I'm looking to execute a shell command in Go and get the resulting output as a string in my program. I saw the Rosetta Code version:

package main
import "fmt"
import "exec"

func main() {
  cmd, err := exec.Run("/bin/ls", []string{"/bin/ls"}, []string{}, "", exec.DevNull, exec.PassThrough, exec.PassThrough)
  if (err != nil) {
    fmt.Println(err)
    return
  }
  cmd.Close()

But this doesn't capture the actual standard out or err in a way that I can programatically access - those still print out to the regular stdout / stderr. I saw that using Pipe as the out or err could help elsewhere, but no example of how to do so. Any ideas?

This answer does not represent the current state of the Go standard library. Please take a look at @Lourenco's answer for an up-to-date method!

Your example does not actually read the data from stdout. This works for me.

package main

import (
   "fmt"
   "exec"
   "os"
   "bytes"
   "io"
)

func main() {
    app := "/bin/ls"
    cmd, err := exec.Run(app, []string{app, "-l"}, nil, "", exec.DevNull, exec.Pipe, exec.Pipe)

    if (err != nil) {
       fmt.Fprintln(os.Stderr, err.String())
       return
    }

    var b bytes.Buffer
    io.Copy(&b, cmd.Stdout)
    fmt.Println(b.String())

    cmd.Close()
}