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Go's Channel and select {} illustrated
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| package main | |
| /* | |
| Channel and select {} illustrated by t9md | |
| =========================================================== | |
| sample program to understand goroutine communication via channel. | |
| based on go-tour's example | |
| https://tour.golang.org/concurrency/5 | |
| */ | |
| import "fmt" | |
| func fibonacci(out, quit chan int) { | |
| x, y := 0, 1 | |
| for { | |
| select { | |
| case out <- x: // if out-ch is available for write(means out-ch's buffer is not full), send next fib number x | |
| x, y = y, x+y | |
| case <-quit: // if some data come to quit-ch, then break inifinite loop by return. | |
| fmt.Println("quit") | |
| return | |
| } | |
| } | |
| } | |
| func main() { | |
| /* | |
| main() start | |
| +-- main() --+ | |
| | | | |
| | | | |
| | | | |
| | | | |
| +------------+ | |
| */ | |
| out := make(chan int) | |
| quit := make(chan int) | |
| /* | |
| two channel (out, quit) created | |
| +-- main() --+ | |
| | |-------------- | |
| | | out<int> | |
| | |-------------- | |
| | |-------------- | |
| | | quit<int> | |
| | |-------------- | |
| +------------+ | |
| */ | |
| // Create anonymous func() and immediately execute as goroutine. | |
| // This function iterate 10 times of (read fib number from out-ch and Println). | |
| // After that, send `0` to quit-ch to notify other fibonacci() to break inifinit loop. | |
| go func() { | |
| for i := 0; i < 10; i++ { | |
| fmt.Println(<-out) // pop data from chan-out 10 times | |
| } | |
| quit <- 0 // then send 0 to quit | |
| }() | |
| /* | |
| +--- main () -------------+ +--- goroutine: func() ---------------+ | |
| | | | | | |
| | | ------------ | for i := 0; i < 10; i++ { | *1 | |
| | | out<int> ====> fmt.Println(<-out) //(*1) | Blocking here for now. | |
| | | ------------ | } | since no data come from out-ch. | |
| | | | | First data will come after fibonacci() start | |
| | | ------------ | | | |
| | | quit<int> <== 0 quit <- 0 | *2 | |
| | | ------------ | | Send 0 to quit-ch for the purpose of break | |
| | | | | inifinit loop of fibonacci() | |
| | | | | | |
| +-------------------------+ +--------------------------------------+ | |
| */ | |
| fibonacci(out, quit) | |
| /* | |
| fibonacci() start, this fibonacci() function inifinitely generate fibonacci | |
| numbers, unless some data is sent to channel 'quit' | |
| +---anonymous func() in main()--+ +-- fibonacci()---------+ | |
| | for i := 0; i < 10; i++ { |------------------- | select { | | |
| | t.Println(<-out) <====== out<int> <== x | case out <- x: | | |
| | } |------------------- | x, y = x, x+y | | |
| | | | | | |
| | | | | | |
| | |------------------- | | | |
| | quit <- 0 0 =======> quit<int> =======> case <- quit: | | |
| | |------------------- | fmt.Println("quit) | | |
| | | | return | | |
| | | | } | | |
| +-------------------------------+ +-----------------------+ | |
| */ | |
| } |
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