[go-nuts] Strange behaviour of Goroutine with time.Sleep on macOS 10.12

[Huy Tr.]

`Hi everybody,

I'm playing around with Goroutine and got a strange issue. 

I tried to run the following code:

package main

import (
    "fmt"
    "time"
)

func loop(c chan int) {
    i := 0
    for {
        time.Sleep(time.Second / 30)
        i = i + 1
        c <- i
    }
}

func main() {
    num := make(chan int)
    go loop(num)
    for {
        select {
        case count := <-num:
            fmt.Printf("Current: %d\n", count)
        }
    }
}


It's just a simple goroutine that execute 30 times per second, and it 
should run forever.

This code run normally on *Mac OS X 10.11 *and *Arch Linux Kernel 4.6.3*

But when I run it on* macOS 10.12 beta 2*, the loop stop updating after 
running for a while.

Go version is *1.6.2* for all environment.

Here is the screen cap: https://www.youtube.com/watch?v=lre18XwZMOo

I also tried to stop it with: 

And this is the output I got, it seems to be stopped at *time.Sleep* 
statement:

SIGABRT: abort
PC=0x56c7b m=0

goroutine 0 [idle]:
runtime.mach_semaphore_wait(0xc800000107, 0xc800000000, 0x1, 0x10000000002c401, 
0xc820000180, 0x1835c0, 0x4b2a9, 0xffffffffffffffff, 0x100000000, 
0x7fff5fbff8ec, ...)
    /usr/local/go/src/runtime/sys_darwin_amd64.s:411 +0xb
runtime.semasleep1(0xffffffffffffffff, 0x100000000)
    /usr/local/go/src/runtime/os1_darwin.go:423 +0xdf
runtime.semasleep.func1()
    /usr/local/go/src/runtime/os1_darwin.go:439 +0x29
runtime.systemstack(0x7fff5fbff8f0)
    /usr/local/go/src/runtime/asm_amd64.s:307 +0xab
runtime.semasleep(0xffffffffffffffff, 0x0)
    /usr/local/go/src/runtime/os1_darwin.go:440 +0x36
runtime.notesleep(0x183a08)
    /usr/local/go/src/runtime/lock_sema.go:166 +0xed
runtime.stopm()
    /usr/local/go/src/runtime/proc.go:1538 +0x10b
runtime.findrunnable(0xc820018000, 0x0)
    /usr/local/go/src/runtime/proc.go:1976 +0x739
runtime.schedule()
    /usr/local/go/src/runtime/proc.go:2075 +0x24f
runtime.park_m(0xc820000180)
    /usr/local/go/src/runtime/proc.go:2140 +0x18b
runtime.mcall(0x7fff5fbffa70)
    /usr/local/go/src/runtime/asm_amd64.s:233 +0x5b

goroutine 1 [chan receive]:
main.main()
    /Users/huy/code/go/sleep/main.go:22 +0x99

goroutine 5 [sleep]:
time.Sleep(0x1fca055)
    /usr/local/go/src/runtime/time.go:59 +0xf9
main.loop(0xc82000e0c0)
    /Users/huy/code/go/sleep/main.go:11 +0x29
created by main.main
    /Users/huy/code/go/sleep/main.go:19 +0x67

rax    0xe
rbx    0x183900
rcx    0x7fff5fbff878
rdx    0x7fff5fbff8f0
rdi    0x107
rsi    0x1835c0
rbp    0x107
rsp    0x7fff5fbff878
r8     0x183900
r9     0xc82001aa00
r10    0xc820019ac0
r11    0x286
r12    0x0
r13    0x27
r14    0x10
r15    0x10f300
rip    0x56c7b
rflags 0x286
cs     0x7
fs     0x0
gs     0x0


Does anybody know why this happen? Is this the issue of the compiler?

Thanks,
Huy

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