You are right, Brian.
The difference is not whether the channel is buffered or unbuffered - while
the receiver is present, none will encounter the deadlock.
package main
import (
"fmt"
"time"
)
//var c = make(chan int)
var c = make(chan int, 2)
func report(){
for{
select{
case n:= <- c:
fmt.Println(n, time.Now().Format("2006-01-02 15:04:05"))
default:
time.Sleep(time.Second)
}
}
}
func main() {
go report()
for i:=1; i<=5; i++{
c <- i
}
}
But obviously, the buffered channel provides another layer of support in
case the receiver is temporarily absent:
package main
import (
"fmt"
"time"
)
//var c = make(chan int)
var c = make(chan int, 5)
func report(){
for{
select{
case n:= <- c:
fmt.Println(n, time.Now().Format("2006-01-02 15:04:05"))
default:
time.Sleep(time.Second)
}
}
}
func main() {
for i:=1; i<=5; i++{
c <- i
}
report()
}
> I made up a work around that just dumps the new message if the buffer is
> full:
>
> You don't need to do that: use select { ... } to check if the channel is
> ready to receive or not.
> https://go.dev/play/p/Mb7VVCTvnfk
>
> But in practice, this is almost never needed, because one goroutine is
> doing the sending and a different goroutine is doing the receiving. The
> sending goroutine blocks until the receiver is ready.
>
> On Wednesday, 13 April 2022 at 09:40:22 UTC+1 yan.z...@gmail.com wrote:
>
>> Since I found if inserting into a buffered channel could cause a crash if
>> it is full already
>> ( now I only use unbuffered channels in work)
>> https://groups.google.com/g/golang-nuts/c/U8lz6noKkuA
>>
>> package main
>>
>> var c = make(chan int, 1)
>>
>> func main() {
>>
>> c <- 1
>> c <- 2 //fatal error: all goroutines are asleep - deadlock!
>> c <- 3
>>
>> }
>>
>> I made up a work around that just dumps the new message if the buffer is
>> full:
>>
>> package main
>>
>> import (
>> "fmt"
>> "sync"
>> )
>>
>> type ChanInt struct{
>> Ch chan int
>> Mu *sync.Mutex
>> }
>>
>> var c = ChanInt{make(chan int, 1), new(sync.Mutex)}
>>
>> func (ch ChanInt) Fill(k int){
>> ch.Mu.Lock()
>> defer ch.Mu.Unlock()
>>
>> if len(ch.Ch) < cap(ch.Ch){
>> ch.Ch <- k
>> }
>> }
>>
>> func main() {
>>
>> fmt.Println("Channel Status: ",len(c.Ch), cap(c.Ch))
>> c.Fill(5)
>> fmt.Println("Channel Status: ", len(c.Ch), cap(c.Ch))
>> fmt.Println("get one out of Channel:", <-c.Ch)
>> fmt.Println("Channel Status: ", len(c.Ch), cap(c.Ch))
>>
>> c.Fill(6)
>> // c.Ch <- 7 //fatal error: all goroutines are asleep - deadlock!
>> c.Fill(7)
>> fmt.Println("Channel Status: ", len(c.Ch), cap(c.Ch))
>> fmt.Println("get one out of Channel:", <-c.Ch)
>> }
>>
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