Hello,
I've written a small program to demonstrate what I am seeing. If I use a
channel as a semaphore and set the size of the channel to 1, I would expect
that the executions of my handle function below would all be executed in
order, but it's not. For some reason the last item in the list is always
handled first, and then the remaining items are handled in order. Does
anyone know why I see this behavior?
Program:
package main
import (
"fmt"
"sync"
"time"
)
var wg sync.WaitGroup
var sem chan int
func handle(i int) {
defer wg.Done()
fmt.Println("waiting: ", i)
sem <- 1
fmt.Println("processing: ", i)
time.Sleep(1 * time.Second)
<-sem
}
func main() {
sem = make(chan int, 1)
nums := []int{1, 2, 3, 4}
for _, i := range nums {
wg.Add(1)
go handle(i)
}
wg.Wait()
}
Output:
waiting: 4
processing: 4
waiting: 1
waiting: 2
waiting: 3
processing: 1
processing: 2
processing: 3
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