func (r *readlineUI) ReadLine(prompt string) (string, error) {
	r.rl.SetPrompt(prompt)
	return r.rl.Readline()
}
ReadLine returns a line of text (a command) read from the user.
prompt is printed before reading the command.
package main
import (
	"fmt"
	"os"
	"strings"
	"syscall"
	"github.com/chzyer/readline"
	"github.com/google/pprof/driver"
)
func main() {
	if err := driver.PProf(&driver.Options{UI: newUI()}); err != nil {
		fmt.Fprintf(os.Stderr, "pprof: %v\n", err)
		os.Exit(2)
	}
}
type readlineUI struct {
	rl *readline.Instance
}
func newUI() driver.UI {
	rl, err := readline.New("")
	if err != nil {
		fmt.Fprintf(os.Stderr, "readline: %v", err)
		return nil
	}
	return &readlineUI{
		rl: rl,
	}
}