go use fsnotify watch file ischanged not working - go

Question

I use the library (http://github.com/fsnotify/fsnotify) to monitor the file system.
I m trying to adjust the repository example to match my requirements, but when i do so the program is not working anymore.
I commented the done channel within the ExampleNewWatcher function
done := make(chan bool)
<-done
As a result, now when i run the example, this channel does not output anything anymore.
event, ok := <-watcher.Events
Complete code：
package main
import (
"github.com/fsnotify/fsnotify"
"log"
"os"
"strconv"
"time"
)
func ExampleNewWatcher() {
watcher, err := fsnotify.NewWatcher()
if err != nil {
log.Fatal(err)
}
defer watcher.Close()
done := make(chan bool) // if i commen this line the `panic` not norking
go func() {
for {
select {
case event, ok := <-watcher.Events:
if !ok {
return
}
log.Println("event:", event)
if event.Op&fsnotify.Write == fsnotify.Write {
log.Println("modified file:", event.Name)
}
panic("just for test") // new output this line
case err, ok := <-watcher.Errors:
if !ok {
return
}
log.Println("error:", err)
}
}
}()
err = watcher.Add("/tmp/foo")
if err != nil {
log.Fatal(err)
}
<-done // comment this
}
func check(err error) {
if err != nil {
panic(err)
}
}
func main() {
// create the test file
var err error
file, err := os.Create("/tmp/foo")
check(err)
_, err = file.Write([]byte("hello world"))
check(err)
stopchan := make(chan struct{})
// test change file
go func() {
for i := 0; i < 10; i++ {
file1, err := os.OpenFile("/tmp/foo", os.O_RDWR, 0644)
check(err)
d := strconv.Itoa(i) + "hello world"
_, err = file1.Write([]byte(d))
check(err)
err = file1.Close()
check(err)
time.Sleep(2 * time.Second) // wait the context writed to the file
}
}()
ExampleNewWatcher() // monitor file
stopchan <- struct{}{}
}