golang select receives close signal anyway

select.go

package main

import "fmt"

func main() {
	var a chan struct{}
		
	fmt.Println("Hello, playground")
	
	a = make(chan struct{})

		
	go func(){
		close(a)	
	}()
		
	fmt.Println("receive1 select")
	select {
			case p:= <-a:	
				fmt.Printf("receive1: %+v\n", p)
				fmt.Println("close received")	
	}
	
	fmt.Println("receive2 select")
	select {
			case p:= <-a:	
				fmt.Printf("receive2: %+v\n", p)
				fmt.Println("close received")	
	}
	

	fmt.Println("closing")
	c:= <-a
	fmt.Printf("closed: %+v\n", c)
}

//http://play.golang.org/p/RxNrLJ_GOa