为什么这样的go代码输出如此？

I'm learning Go langue in here, and I modify a little code like this, I add a sleep(2s) before quit <- 0, and output index of fibonacci with i, below is my code:

package main

import "fmt"
import "time"

func fibonacci(c, quit chan int) {
    x, y := 0, 1
    for {
        select {
        case c <- x:
            x, y = y, x+y
        case <-quit:
            fmt.Println("quit")
            return
        }
    }
}

func main() {
    c := make(chan int)
    quit := make(chan int)
    go func() {
        for i := 0; i < 10; i++ {
            fmt.Println(i,<-c) // output index for result clearly
        }
        time.Sleep(2000*time.Millisecond) // add sleep for result clearly
        quit <- 0
    }()
    fibonacci(c, quit)
}

I find the stdout output 0-8 immediately, but wait 2 seconds it output 9th and then is "quit".

I move this code to a single go file and run it. At first it output 0-8 like above described, but after I change total number (from 10 to 9,8 or 3, whatever) some times, it output directly all fibonacci number immediately as I was excepted (of course it output quit after 2 seconds)!

I run the code in the browser (I used Chrome) it still output 9th delay, when I change 10 to 3, it output 0-2 immediately.

So I'm confused why does it output 9th delay?

UPDATE: I think I know why, because my output window too small to output whole result, but I always scroll down all time it still display 8th. If I scale output window larger, it will output 0-9 immediately. So is it a bug of this tutorial?

I think it is a bug of this tutorial. If the output window (left-bottom) is too small, it will display without the last line, so the 9th won't be display immediately.

if I add fmt.Println("foo") after fmt.Println(i,<-c), it won't output the last line contains foo string, but the 9th fibonacci will be displayed.

I capture the response in Chrome, it can tell how to display the result including what time it will output. So it must be a bug of page that swallow the last line. :D

PS: The response like this:

{
   "Errors":"",
   "Events":[
      {
         "Message":"0 0
foo
1 1
foo
2 1
foo
3 2
foo
4 3
foo
5 5
foo
6 8
foo
7 13
foo
8 21
foo
9 34
foo
",
         "Kind":"stdout",
         "Delay":0
      },
      {
         "Message":"quit
",
         "Kind":"stdout",
         "Delay":2000000000
      }
   ]
}