Gocui breaks after pager program.

gocui-pager.go

package main

import (
	"fmt"
	"log"
	"os/exec"
	"os"
	"strings"
	"github.com/jroimartin/gocui"
	"time"
	"sync"
	"bytes"
)

var (
	done = make(chan struct{})
	wg  sync.WaitGroup
)

func main() {
	g, err := gocui.NewGui(gocui.OutputNormal)
	if err != nil {
		log.Panicln(err)
	}
	defer g.Close()

	g.SetManagerFunc(layout)

	if err := g.SetKeybinding("", gocui.KeyCtrlC, gocui.ModNone, quit); err != nil {
		log.Panicln(err)
	}
	if err := g.SetKeybinding("", gocui.KeySpace, gocui.ModNone, pager); err != nil {
		log.Panicln(err)
	}

	wg.Add(1)
	go showTime(g)

	if err := g.MainLoop(); err != nil && err != gocui.ErrQuit {
		log.Panicln(err)
	}

	wg.Wait()
}

func layout(g *gocui.Gui) error {
	maxX, _ := g.Size()
		if v, err := g.SetView("main", -1, -1, maxX/2-1, 4); err != nil {
		if err != gocui.ErrUnknownView {
			return err
		}
		fmt.Fprintln(v, time.Now().Format("2006-01-02 15:04:05.000"))
		v.Frame = false
	}

	return nil
}

func pager(g *gocui.Gui, v *gocui.View) error {
	var buf bytes.Buffer
	for i:=0; i < 10; i++ {
		buf.WriteString(fmt.Sprintf("%d -- %s %s\n", i, "example", "text"))
	}

	cmd := exec.Command("less")
	cmd.Stdin = strings.NewReader(buf.String())
	cmd.Stdout = os.Stdout
	err := cmd.Run()

	return err
}

func showTime(g *gocui.Gui) {
	defer wg.Done()

	for {
		select {
		case <-done:
			return
		case <-time.After(1 * time.Second):
			t := time.Now()

			g.Update(func(g *gocui.Gui) error {
				v, err := g.View("main")
				if err != nil {
					return err
				}
				v.Clear()
				fmt.Fprintln(v, t.Format("2006-01-02 15:04:05.000"))
				return nil
			})
		}
	}
}

func quit(g *gocui.Gui, v *gocui.View) error {
	close(done)
	return gocui.ErrQuit
}