===== HTTP Client (net/http) =====

==== What is it? ====
An **HTTP client** is code that sends HTTP requests to a server and reads HTTP responses back.

In Go, the standard library package `net/http` provides:
  * helper functions like `http.Get`, `http.Post`, and
  * the configurable client type `http.Client`.

==== What is it used for? ====
  * Call external REST APIs.
  * Send webhooks.
  * Download/upload data over HTTP/HTTPS.
  * Communicate between microservices.

==== Core building blocks ====
  * **Client**: performs requests (`Do`, `Get`, `Post`).
  * **Request**: method, URL, headers, body, context.
  * **Response**: status, headers, body.
  * **Transport**: controls connection pooling, proxies, TLS, timeouts (advanced).

==== Minimal example (GET) ====
<code go>
package main

import (
    "io"
    "log"
    "net/http"
)

func main() {
    resp, err := http.Get("https://example.com")
    if err != nil {
        log.Fatal(err)
    }
    defer resp.Body.Close()

    b, _ := io.ReadAll(resp.Body)
    log.Println("status:", resp.Status)
    log.Println("bytes:", len(b))
}
</code>

==== Best practices (important) ====
  * Always `defer resp.Body.Close()` to avoid leaking connections.
  * Reuse an `http.Client` for many requests (do not create a new one every time).
  * Use timeouts (client timeout or request context) to avoid hanging forever.
  * Validate status codes before trusting the response body.

==== Related pages ====
  * [[go:stdlib:http_server|HTTP server overview]]
  * [[go:stdlib:http_client_struct|http.Client]]
  * [[go:stdlib:http_server_struct|http.Server]]
  * [[go:concurrency:context|context.Context]]

==== Hard words (English) ====
  * **client** /ˈklaɪənt/: phía gọi (bên gửi request)
  * **request** /rɪˈkwest/: yêu cầu
  * **response** /rɪˈspɑːns/: phản hồi
  * **leak** /liːk/: rò rỉ (tài nguyên/kết nối)
  * **reuse** /ˌriːˈjuːz/: tái sử dụng
  * **timeout** /ˈtaɪmaʊt/: hết thời gian chờ
  * **hanging** /ˈhæŋɪŋ/: treo/chờ mãi
  * **transport** /ˈtrænspɔːrt/: tầng vận chuyển (cách kết nối HTTP)
  * **pooling** /ˈpuːlɪŋ/: gom/tái sử dụng (kết nối)