Как проверить ошибку тайм-аута http в Go?

В настоящее время вы бы не сделали этого таким образом, и установка тайм-аута на клиенте остается в соответствии с гарантией стабильности API .

Сегодня вы настроили клиент и выполнили запрос с контекстом .WithTimeout .

TL;DR: контекст будет «Готово», если время ожидания запроса истекло до получения ответа, и не будет «Готово», если ответ будет возвращен до истечения времени ожидания.

package main

import (
    "context"
    "io"
    "log"
    "net/http"
    "net/url"
    "time"
)

func main() {

    // Start a http server to test the timeout
    srv := setupServer()
    defer srv.Shutdown(context.Background())

    // Examle 1: Using a context with a timeout for a request
    // =======================================================

    // create a default http client
    client := &http.Client{}
    ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)

    // Release resources when done
    defer cancel()

    // Create a new request with our context
    req, _ := http.NewRequestWithContext(ctx, "GET", "http://localhost:8080/hellotimeout", nil)

    // Start a timer
    start := time.Now()
    // Make the request
    _, err := client.Do(req)

    // Check if the request was anything other than a timeout
    // Note that we could check for the timeout error here.
    // However, we will use a select statement to demonstrate how to handle the timeout.
    if urlErr, isURLErr := err.(*url.Error); isURLErr && !urlErr.Timeout() {
        log.Printf("Something went wrong: %s", urlErr)
        return
    }

    select {
    // If the request times out, the context will be done.
    // If the request is completed here, the context will not be done and the default case will be executed.
    case <-ctx.Done():
        log.Printf("Request timed out after %s", time.Since(start))
    default:
        log.Printf("Request completed after %s", time.Since(start))
        log.Println("Processing response...")
    }

    // Examle 2: The same, but this time the request does not timeout
    // ==============================================================

    // Create a new request with our context
    ctx2, cancel2 := context.WithTimeout(context.Background(), 3*time.Second)
    defer cancel2()
    req, _ = http.NewRequestWithContext(ctx2, "GET", "http://localhost:8080/hello", nil)

    // Start a timer
    start = time.Now()
    // Make the request
    resp, err := client.Do(req)

    // Check if the request was anything other than a timeout
    if urlErr, isURLErr := err.(*url.Error); isURLErr && !urlErr.Timeout() {
        log.Printf("Something went wrong: %s", urlErr)
        return
    }

    select {
    case <-ctx2.Done():
        log.Printf("Request timed out after %s", time.Since(start))
        return
    default:
        log.Printf("Request completed after %s", time.Since(start))
    }
    log.Println("Processing response...")
    io.Copy(log.Writer(), resp.Body)
}

func setupServer() *http.Server {
    // Setup a server so we can test the timeout
    srv := &http.Server{Addr: ":8080"}

    http.Handle("/hellotimeout", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Simulate a long running request
        time.Sleep(5 * time.Second)
        w.Write([]byte("Hello, World!"))
    }))

    http.Handle("/hello", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Respond immediately
        w.Write([]byte("Hello, World!"))
    }))

    // Start the server in "background"

    go srv.ListenAndServe()
    return srv
}

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