Context Timeout HTTP Client Request

package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"time"
)

type Shipment struct {
	ID     string `json:"id"`
	Status string `json:"status"`
}

func queryShipment(ctx context.Context, baseURL, id string) (*Shipment, error) {
	ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
	defer cancel() // 必须释放计时器资源

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, baseURL+"/shipments/"+id, nil)
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	req.Header.Set("Accept", "application/json")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		if errors.Is(err, context.DeadlineExceeded) {
			return nil, fmt.Errorf("shipment %s timed out after 3s: %w", id, err)
		}
		return nil, fmt.Errorf("request failed: %w", err)
	}
	defer resp.Body.Close()

	var shipment Shipment
	if err := json.NewDecoder(resp.Body).Decode(&shipment); err != nil {
		return nil, fmt.Errorf("decode body: %w", err)
	}
	return &shipment, nil
}

func main() {
	s, err := queryShipment(context.Background(), "https://api.example.com", "sh-1")
	fmt.Println(s, err)
}