Reallocate stdin after injecting file/buffer to cmd

main.go

package main

import (
	"os"
	"os/exec"
  "io"
	"strings"
	"github.com/kr/pty"
)

// This will be the equivalent of (echo id; cat) | /bin/sh but nicer
// because it realocates a tty after.

func main() {
	buffer := strings.NewReader("id\n")
	reader := io.MultiReader(buffer, os.Stdin)

	cmd := exec.Command("/bin/sh")
	tty, _ := pty.Start(cmd)
	defer tty.Close()

	go func() {
		io.Copy(tty, reader)
	}()
	go func() {
		io.Copy(os.Stdout, tty)
	}()

	cmd.Wait()
}