HTTP JSON request with a context timeout

package main

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

// GetJSON fetches and decodes JSON with a deadline and a response size cap.
func GetJSON(ctx context.Context, client *http.Client, url string, target any) error {
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

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

	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("get %s: %w", url, err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("get %s: status %d", url, resp.StatusCode)
	}
	return json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(target)
}

func main() {
	var payload map[string]any
	_ = GetJSON(context.Background(), http.DefaultClient, "https://httpbin.org/json", &payload)
}