Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

package main

import (
    "fmt"
    "math/rand"
    "time"
)

func slowOp(id int) <-chan string {
    ch := make(chan string)
    go func() {
        delay := time.Duration(rand.Intn(300)) * time.Millisecond
        time.Sleep(delay)
        ch <- fmt.Sprintf("result from op %d (took %v)", id, delay)
    }()
    return ch
}

// fanIn merges multiple channels into one
func fanIn(cs ...<-chan string) <-chan string {
    merged := make(chan string)
    for _, c := range cs {
        c := c // capture
        go func() {
            for v := range c {
                merged <- v
            }
        }()
    }
    return merged
}

func main() {
    // Select with timeout
    ch := slowOp(1)
    select {
    case result := <-ch:
        fmt.Println(result)
    case <-time.After(150 * time.Millisecond):
        fmt.Println("timed out waiting for op 1")
    }

// Non-blocking receive with default
    ready := make(chan int, 1)
    select {
    case v := <-ready:
        fmt.Println("got:", v)
    default:
        fmt.Println("nothing ready, continuing")
    }

// Fan-in from multiple goroutines
    merged := fanIn(slowOp(2), slowOp(3), slowOp(4))
    timeout := time.After(400 * time.Millisecond)
    for i := 0; i < 3; i++ {
        select {
        case msg := <-merged:
            fmt.Println(msg)
        case <-timeout:
            fmt.Println("overall timeout reached")
            return
        }
    }
}