Go Junior (0–2 yrs) Coding Frequent Go goroutines channels HTTP fan-out

Write a Go function that fans out HTTP requests using goroutines and collects results via channels

go-jun-002

Your answer

Answer as you would in a real interview — explain your thinking, not just the conclusion.

Model answer

I spawn one goroutine per URL, each writing its result to a buffered channel sized to the number of URLs so goroutines never block. A result struct carries the URL, status code, and any error so the caller knows which request failed. After all goroutines launch, I drain the channel exactly len(urls) times. This is simpler than sync.WaitGroup for result collection because the channel itself serialises all responses into one place.

Code example

package main

import (
    "fmt"
    "net/http"
)

type Result struct {
    URL    string
    Status int
    Err    error
}

func fetchAll(urls []string) []Result {
    ch := make(chan Result, len(urls))
    for _, url := range urls {
        go func(u string) {
            resp, err := http.Get(u)
            if err != nil {
                ch <- Result{URL: u, Err: err}
                return
            }
            defer resp.Body.Close()
            ch <- Result{URL: u, Status: resp.StatusCode}
        }(url)
    }
    results := make([]Result, len(urls))
    for i := range results {
        results[i] = <-ch
    }
    return results
}

func main() {
    urls := []string{"https://example.com", "https://go.dev"}
    for _, r := range fetchAll(urls) {
        fmt.Printf("%s -> %d %v\n", r.URL, r.Status, r.Err)
    }
}

Follow-up

How would you add a timeout so the function returns after 5 seconds even if some requests are still in-flight?