package main
import (
"fmt"
"time"
)
func main() {
start := time.Now()
doneChan := make(chan bool)
params := make(chan int, 5)
params <- 1
params <- 2
params <- 3
params <- 4
params <- 5
// close channel, there is no new value send to this channel.
// NOTE : Even when channel is closed, go routine can still receive msg, but block for sent msg
// When using `range` to get msg from channel, we need to close channel to indicate that there is no value.
// If not closed, then `range` will continue to listen to the open channel
close(params)
pipeline(params, doneChan)
select {
case done := <-doneChan:
elapsed := time.Since(start)
fmt.Println("DONE", done, elapsed)
}
}
func pipeline(params <-chan int, doneChan chan bool) {
go func() {
for _ = range step3(step2(step1(params))) {
//fmt.Println(result)
}
doneChan <- true // mark as done, so it could trigger `select case done`
close(doneChan) // close channel, all process has been completed
}()
}
func step1(params <-chan int) <-chan string {
ch := make(chan string, len(params))
go func() {
for param := range params {
time.Sleep(1 * time.Second)
result := fmt.Sprintf("step1(%v)", param)
fmt.Println(result)
ch <- result
}
close(ch) // close channel
}()
return ch
}
func step2(params <-chan string) <-chan string {
ch := make(chan string, len(params))
go func() {
for param := range params {
time.Sleep(1 * time.Second)
result := fmt.Sprintf("step2(%v)", param)
fmt.Println(result)
ch <- result
}
close(ch) // close channel
}()
return ch
}
func step3(params <-chan string) <-chan string {
ch := make(chan string, len(params))
go func() {
for param := range params {
time.Sleep(1 * time.Second)
result := fmt.Sprintf("step3(%v)", param)
fmt.Println(result)
ch <- result
}
close(ch) // close channel
}()
return ch
}
output
step1(1)
step2(step1(1))
step1(2)
step2(step1(2))
step1(3)
step3(step2(step1(1)))
step1(4)
step2(step1(3))
step3(step2(step1(2)))
step2(step1(4))
step3(step2(step1(3)))
step1(5)
step3(step2(step1(4)))
step2(step1(5))
step3(step2(step1(5)))
DONE true 7s
Process finished with exit code 0