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golang的channel 这个行为很奇怪

有点奇怪，记录一下：

下面这个图执行了3个

package main
 
import (
  "fmt"
)
 
func main() {
  c := make(chan string)
 
  for i := 0; i < 5; i++ {
    go func(i int) {
      msg := <- c
      c <- fmt.Sprintf("%s, hi from %d", msg, i)
    }(i)
  }
 
  c <- "original"
 
  fmt.Println(<-c)
}

--------------------------------------

// This sample program demonstrates how to use an unbuffered
// channel to simulate a game of tennis between two goroutines.
package main
 
import (
    "fmt"
    "math/rand"
    "sync"
    "time"
)
 
// wg is used to wait for the program to finish.
var wg sync.WaitGroup
 
func init() {
    rand.Seed(time.Now().UnixNano())
}
 
// main is the entry point for all Go programs.
func main() {
    // Create an unbuffered channel.
    court := make(chan int)
 
    // Add a count of two, one for each goroutine.
    wg.Add(2)
 
    // Launch two players.
    go player("Nadal", court)
    go player("Djokovic", court)
 
    // Start the set.
    court <- 1
 
    // Wait for the game to finish.
    wg.Wait()
}
 
// player simulates a person playing the game of tennis.
func player(name string, court chan int) {
    // Schedule the call to Done to tell main we are done.
    defer wg.Done()
 
    for {
        // Wait for the ball to be hit back to us.
        ball, ok := <-court
        if !ok {
            // If the channel was closed we won.
            fmt.Printf("Player %s Won\n", name)
            return
        }
 
        // Pick a random number and see if we miss the ball.
        n := rand.Intn(100)
        if n%13 == 0 {
            fmt.Printf("Player %s Missed\n", name)
 
            // Close the channel to signal we lost.
            close(court)
            return
        }
 
        // Display and then increment the hit count by one.
        fmt.Printf("Player %s Hit %d\n", name, ball)
        ball++
 
        // Hit the ball back to the opposing player.
        court <- ball
    }
}