io tee problem

tee.go

package main

import (
	"flag"
	"fmt"
	"io"
	"time"
)

func newReader() io.Reader {
	pr, pw := io.Pipe()
	go func() {
		for {
			s := fmt.Sprint(time.Now().UnixNano())
			pw.Write([]byte(s))
			time.Sleep(time.Second)
		}
	}()
	return pr
}

func read(source string, r io.Reader, notRead bool) {
	if notRead {
		time.Sleep(time.Hour)
	}
	buff := make([]byte, 1e3)
	for {
		n, err := r.Read(buff)
		if err != nil {
			break
		}
		fmt.Printf("read from [%s]: %s\n", source, buff[:n])
	}
}

func main() {

	mode := flag.Int("mode", 1, "1=read all; 2=not read teeReader; 3=not read pipeReader")
	flag.Parse()

	oriReader := newReader()

	pipeReader, pw := io.Pipe()
	teeReader := io.TeeReader(oriReader, pw)

	switch *mode {
	case 1:
		fmt.Println("read all (mode 1)")
		go read("teeReader", teeReader, false)
		go read("pipeReader", pipeReader, false)

	case 2:
		fmt.Println("not read teeReader (mode 2)")
		// change the order will solve it but no outputs neither
		read("pipeReader", pipeReader, false)
		go read("teeReader", teeReader, true)

	case 3:
		fmt.Println("not read pipeReader (mode 3)")
		// change the order will solve it but no outputs neither
		read("teeReader", teeReader, false)
		go read("pipeReader", pipeReader, true)
	}

	c := make(chan bool)
	<-c
}