Add select nil chan 3

Author: devlights

examples/basic/goroutines/examples.go

@@ -23,6 +23,7 @@ func (r *register) Regist(m mapping.ExampleMapping) {
 	m["goroutines_with_context_timeout"] = WithContextTimeout
 	m["goroutines_select_nil_chan_1"] = SelectNilChan1
 	m["goroutines_select_nil_chan_2"] = SelectNilChan2
+	m["goroutines_select_nil_chan_3"] = SelectNilChan3
 	m["goroutines_using_chan_semaphore"] = UsingChanSemaphore
 	m["goroutines_using_mutex"] = UsingMutex
 	m["goroutines_with_context_deadline"] = WithContextDeadline

examples/basic/goroutines/selectnilchan3.go

@@ -0,0 +1,58 @@
+package goroutines
+
+import "github.com/devlights/gomy/output"
+
+// SelectNilChan3 -- select ステートメントで nil チャネル を使って選択されるチャネルの有効・無効を切り替えるサンプルです (3).
+//
+// シンプルな形のサンプル。
+func SelectNilChan3() error {
+	var (
+		gen = func(out chan<- int) {
+			defer close(out)
+			for i := 0; i < 5; i++ {
+				out <- (i + 1)
+			}
+		}
+		output = func(done chan<- any, in1, in2 <-chan int) {
+			defer close(done)
+
+		LOOP:
+			for {
+				select {
+				case v, ok := <-in1:
+					if !ok {
+						in1 = nil
+						output.Stderrl("[in1]", "close")
+						continue
+					}
+					output.Stderrl("[in1]", v)
+				case v, ok := <-in2:
+					if !ok {
+						in2 = nil
+						output.Stderrl("[in2]", "close")
+						continue
+					}
+					output.Stderrl("[in2]", v)
+				default:
+					if in1 == nil && in2 == nil {
+						break LOOP
+					}
+				}
+			}
+		}
+	)
+
+	var (
+		ch1  = make(chan int)
+		ch2  = make(chan int)
+		done = make(chan any)
+	)
+
+	go gen(ch1)
+	go gen(ch2)
+	go output(done, ch1, ch2)
+
+	<-done
+
+	return nil
+}