more examples

example-go-channel/5threads.go

@@ -0,0 +1,45 @@
+// https://www.digitalocean.com/community/tutorials/how-to-run-multiple-functions-concurrently-in-go
+// who came up with the idea of making community tutorials. that was a good idea!
+
+package main
+
+import (
+	"fmt"
+	"sync"
+)
+
+func generateNumbers(total int, ch chan<- int, wg *sync.WaitGroup) {
+	defer wg.Done()
+
+	for idx := 1; idx <= total; idx++ {
+		fmt.Printf("START sending %d to channel\n", idx)
+		ch <- idx
+	}
+}
+
+func printInt(idx int, ch <-chan int, wg *sync.WaitGroup) {
+	defer wg.Done()
+
+	for num := range ch {
+		fmt.Printf("%d: read %d from channel\n", idx, num)
+	}
+}
+
+func main() {
+	var wg sync.WaitGroup
+	numberChan := make(chan int)
+
+	for idx := 1; idx <= 5; idx++ {
+		fmt.Printf("START printInt %d\n", idx)
+		wg.Add(1)
+		go printInt(idx, numberChan, &wg)
+	}
+
+	generateNumbers(20, numberChan, &wg)
+
+	close(numberChan)
+
+	fmt.Println("Waiting for goroutines to finish...")
+	wg.Wait()
+	fmt.Println("Done!")
+}

example-go-channel/Makefile

@@ -1,3 +1,6 @@
 build:
-	GO111MODULE="off" go build -v -x
-	./go-channels
+	GO111MODULE="off" go build -v -x -o ~/go/bin/5threads 5threads.go
+	5threads
+
+simple:
+	GO111MODULE="off" go build -v -x -o ~/go/bin/simple-worker simple-worker.go

example-go-channel/main.go

@@ -12,9 +12,12 @@ func generateNumbers(total int, ch chan<- int, wg *sync.WaitGroup) {
 	defer wg.Done()
 
 	for idx := 1; idx <= total; idx++ {
-		fmt.Printf("sending %d to channel\n", idx)
+		fmt.Printf("START sending %d to channel\n", idx)
 		ch <- idx
+		fmt.Printf("END sending %d to channel\n", idx)
 	}
+	wg.Wait()
+	fmt.Printf("END wg sending to channel\n")
 }
 
 func printInt(idx int, ch <-chan int, wg *sync.WaitGroup) {

example-go-channel/simple-worker.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+    "fmt"
+    "sync"
+    "time"
+)
+
+func worker(id int) {
+    fmt.Printf("Worker %d starting\n", id)
+
+    time.Sleep(time.Second)
+    fmt.Printf("Worker %d done\n", id)
+}
+
+func main() {
+
+    var wg sync.WaitGroup
+
+    for i := 1; i <= 5; i++ {
+        wg.Add(1)
+
+        i := i
+
+        go func() {
+            defer wg.Done()
+            worker(i)
+        }()
+    }
+
+    wg.Wait()
+
+}