I'm not able to close channel when there is no knowledge about its
length
package main
import (
"fmt"
"time"
)
func gen(ch chan int) {
var i int
for {
time.Sleep(time.Millisecond * 10)
ch <- i
i++
// when no more data (e.g. from db, or event stream)
if i > 100 {
break
}
}
// hot to close it properly?
close(ch)
}
func receiver(ch chan int) {
for i := range ch {
fmt.Println("received:", i)
}
}
func main() {
ch := make(chan int)
for i := 0; i < 10; i++ {
go gen(ch)
}
receiver(ch)
}
It gives me error
panic: send on closed channel
goroutine 8 [running]:
main.gen(0xc82001a0c0)
/home/exu/src/github.com/exu/go-workshops/100-concurrency-channels/16-close-problem.go:12 +0x57
created by main.main
/home/exu/src/github.com/exu/go-workshops/100-concurrency-channels/16-close-problem.go:35 +0xbd
goroutine 1 [panicwait]:
runtime.gopark(0x0, 0x0, 0x50b8e0, 0x9, 0x10, 0x1)
/usr/lib/go/src/runtime/proc.go:185 +0x163
runtime.main()
/usr/lib/go/src/runtime/proc.go:121 +0x2f4
runtime.goexit()
/usr/lib/go/src/runtime/asm_amd64.s:1696 +0x1
goroutine 6 [sleep]:
time.Sleep(0x989680)
/usr/lib/go/src/runtime/time.go:59 +0xf9
main.gen(0xc82001a0c0)
/home/exu/src/github.com/exu/go-workshops/100-concurrency-channels/16-close-problem.go:11 +0x29
created by main.main
/home/exu/src/github.com/exu/go-workshops/100-concurrency-channels/16-close-problem.go:33 +0x79
goroutine 7 [sleep]:
time.Sleep(0x989680)
/usr/lib/go/src/runtime/time.go:59 +0xf9
main.gen(0xc82001a0c0)
/home/exu/src/github.com/exu/go-workshops/100-concurrency-channels/16-close-problem.go:11 +0x29
created by main.main
/home/exu/src/github.com/exu/go-workshops/100-concurrency-channels/16-close-problem.go:34 +0x9b
exit status 2
It's logical - first goroutine closing channel when the second one tries to send to it. What will be the best approach to close channel in this situation?
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