===== HTTP Server (net/http) =====

==== What is it? ====
An HTTP server is a program that listens on a network address (host:port) and serves HTTP requests by calling a handler.

In Go, the standard library package `net/http` provides everything you need to build a basic server.

==== What is it used for? ====
  * Build REST APIs and web services.
  * Serve pages, JSON responses, files, health checks.
  * Handle routing via `ServeMux` or a custom router.

==== Core building blocks ====
  * **Handler**: code that handles a request and writes a response.
    * `http.Handler` interface
    * `http.HandlerFunc` adapter
  * **ResponseWriter**: used to write status code, headers, and body.
  * **Request**: contains method, URL, headers, body, context, etc.
  * **ServeMux**: request multiplexer (router) that maps paths to handlers.
    * `http.DefaultServeMux` is the default global mux.

==== Minimal server (Hello + health) ====
<code go>
package main

import (
    "log"
    "net/http"
)

func main() {
    mux := http.NewServeMux()

    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("hello"))
    })

    mux.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
        w.WriteHeader(http.StatusOK)
        w.Write([]byte("ok"))
    })

    log.Println("listening on :8080")
    log.Fatal(http.ListenAndServe(":8080", mux))
}
</code>

==== Production notes (important) ====
For production, you often use `http.Server` to set timeouts and graceful shutdown.

Example fields:
  * `ReadHeaderTimeout`
  * `ReadTimeout`
  * `WriteTimeout`
  * `IdleTimeout`

==== Related pages ====
  * [[go:stdlib:http_server_listenandserve|http.ListenAndServe]]
  * [[go:stdlib:middleware|Middleware]]
  * [[go:stdlib:http_client|HTTP client]]
  * [[go:stdlib:httptest|httptest]]

==== Hard words (English) ====
  * **listen** /ˈlɪsən/: lắng nghe (mở cổng nhận kết nối)
  * **serve** /sɝːv/: phục vụ request/response
  * **handler** /ˈhændlər/: bộ xử lý request
  * **interface** /ˈɪntərfeɪs/: giao diện (hợp đồng hàm)
  * **adapter** /əˈdæptər/: bộ chuyển/đệm để khớp kiểu
  * **multiplexer (mux)** /ˈmʌltɪˌpleksər/: bộ “chuyển tuyến”/gom chọn route
  * **routing** /ˈruːtɪŋ/: định tuyến
  * **graceful shutdown** /ˈɡreɪsfəl ˈʃʌtdaʊn/: tắt êm (xử lý xong rồi tắt)
  * **timeout** /ˈtaɪmaʊt/: hết thời gian chờ