Go Concurrency Patterns - Pattern #2

In the video Google I/O 2012 - Go Concurrency Patterns, Rob Pike introduced the Multiplexing Pattern at about 17:00 in the video. Using the fanIn() function, whoever is ready will talk first.

But when I assemble the program in here - play.golang.org/p/cvAi5MAAKT, it always run in sequence as

NumCPU:  4  //Edit#1 output
Joe 0
Ann 0
Joe 1
Ann 1
Joe 2
Ann 2
Joe 3
Ann 3
Joe 4
Ann 4
You're both boring: I'm leaving

What's wrong with this code?

package main
import "fmt"
import "time"
import "math/rand"
//Pattern #2
//Multiplexing
func fanIn(in1, in2 <-chan string) <-chan string {
	c := make(chan string)
	go func() {for {c <- <-in1}}()
	go func() {for {c <- <-in2}}()
	return c
}
func boring(msg string) <-chan string {
	c := make(chan string)
	go func() {
		for i := 0; ; i++ {
			c <- fmt.Sprintf("%s %d\n", msg, i)
			time.Sleep(time.Duration(rand.Intn(1e3)) * time.Millisecond)
		}
	}()
	return c
}
func main() {
    //Edit#1 according to the first answer, add following two lines
    fmt.Println("NumCPU: ", runtime.NumCPU())
    runtime.GOMAXPROCS(runtime.NumCPU())
	c := fanIn(boring("Joe"), boring("Ann"))
	for i := 0; i < 10; i++ {
		fmt.Println(<-c)
	}
	fmt.Println("You're both boring: I'm leaving")
}

Update1:
According to the answer, I've changed the code, but the result is still the same. I'm using windows 7. See the changes above in "Edit#1".

Update2:

I found the answer: Just increase the loop number to a larger number(say 40), it will show out the different orders even if the GOMAXPROCS use the default value. You can try it from the playground.

Nothing is wrong, you just haven't told the Go runtime to use more than one thread. Set the GOMAXPROCS environment variable*, or use the runtime package's runtime.GOMAXPROCS function. GOMAXPROCS determines the number of OS threads the Go runtimes creates to multiplex goroutines that you create over. If GOMAXPROCS is 1 (the default), you will often see very deterministic looking behaviour.

For example when running your program:

GOMAXPROCS=4 ./myProgram

For example in your program:

runtime.GOMAXPROCS(runtime.NumCPU())

P.S. *If you are using the playground and not your own machine, GOMAXPROCS will always be 1.