Deadlock in channel

Situation 1 ： In the case of a single thread , Go to channel The amount of data put in exceeds its channel When it comes to the size of

func main(){
    
	var ch = make(chan int, 2)
	ch <- 2
	ch <- 3
	ch <- 8
}

The errors that occur are as follows ：

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan send]:
main.main()
        /Users/lcq/go/src/go_base/gochanneldemo/channeldemo.go:32 +0x8d

Situation two ： In the case of a single thread , hold channel After all the data in is taken out , Continue to get data

func main(){
    
	var ch = make(chan int, 2)
	ch <- 2
	ch <- 3
	// ch <- 8
	//  Start fetching data 
	fmt.Println(<-ch)
	fmt.Println(<-ch)
	fmt.Println(<-ch)
}

Error is as follows ：

2
3
fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan receive]:
main.main()
        /Users/lcq/go/src/go_base/gochanneldemo/channeldemo.go:36 +0x1c6

Situation three ： channel Without closing , Use for range Traversal

func main(){
    
	var ch = make(chan int, 3)
	ch <- 2
	ch <- 3
	// close(ch)
	// for range Traverse   Also is to channel From the data in 
	for val := range ch{
    
		fmt.Println(val)
	}
	// fmt.Println(<-ch)
}

Error is as follows ：

2
3
fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan receive]:
main.main()
        /Users/lcq/go/src/go_base/gochanneldemo/channeldemo.go:60 +0xfd