feat(go): introduce Go module with basic example using channels

- Add `go.mod` file for Go module initialization
- Create `main.go` with a basic example of using channels and timeouts in Go

Signed-off-by: appleboy <[email protected]>

Author: appleboy

example56-context-timeout/go.mod

@@ -0,0 +1,3 @@
+module example
+
+go 1.23.1

example56-context-timeout/main.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"time"
+)
+
+func main() {
+	output := make(chan int, 1)
+
+	go func() {
+		for i := 0; i < 30; i++ {
+			output <- i
+			time.Sleep(100 * time.Millisecond)
+		}
+	}()
+
+	for {
+		select {
+		case val := <-output:
+			println("output:", val)
+		// how to fix the timeout issue?
+		case <-time.After(1 * time.Second):
+			println("timeout")
+			return
+		}
+	}
+}