Hi
Here is the code:
Version 1:
package main
import (
"fmt"
"sync"
)
var a string
var once sync.Once
func setup() {
a = "hello,world\n"
}
func doprint() {
once.Do(setup)
fmt.Print(a)
}
func twoprint() <-chan struct{} {
var wg sync.WaitGroup
wg.Add(2)
ch := make(chan struct{})
go func() {
doprint()
wg.Done()
}()
go func() {
doprint()
wg.Done()
}()
go func() {
wg.Wait()
close(ch)
}()
return ch
}
func main() {
ch := twoprint()
<-ch
}
Version 2:
package main
import (
"fmt"
"sync"
)
var a string
var once sync.Once
func setup() {
a = "hello,world\n"
}
func doprint() {
once.Do(setup)
fmt.Print(a)
}
func twoprint() {
var wg sync.WaitGroup
wg.Add(2)
go func() {
doprint()
wg.Done()
}()
go func() {
doprint()
wg.Done()
}()
wg.Wait()
}
func main() {
twoprint()
}
Cheers snmed
Am Donnerstag, 2. November 2017 10:37:15 UTC+1 schrieb 28911...@gmail.com:
>
> Sorry,I try my best to open the website but it can't work.Can you write it
> ??Thank you so much.
>
> 在 2017年10月30日星期一 UTC+8下午4:29:44，snmed写道：
>>
>> Hi
>>
>> There are several ways to solve it, here are two of them:
>>
>> https://play.golang.org/p/wJwkI7HQwv
>> https://play.golang.org/p/nasUcgBeG4
>>
>> I prefer the first one, because so I can decide if i want to wait for the
>> end of twoprint or not.
>>
>> Cheers
>>
>> Am Montag, 30. Oktober 2017 06:43:45 UTC+1 schrieb 28911...@gmail.com:
>>>
>>> Yes, you're right.So how to solve it??
>>>
>>> 在 2017年10月30日星期一 UTC+8下午12:37:49，Dave Cheney写道：
>>>>
>>>> Hello. I’m guessing that your tried calling twoprint(), but you’ve
>>>> probably found that nothing is printed to the screen before your program
>>>> exits.
>>>>
>>>> Is that correct?
>>>
>>>
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