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.

• Build REST APIs and web services.
• Serve pages, JSON responses, files, health checks.
• Handle routing via `ServeMux` or a custom router.

• 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.

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))
}

For production, you often use `http.Server` to set timeouts and graceful shutdown.

Example fields:

• `ReadHeaderTimeout`
• `ReadTimeout`
• `WriteTimeout`
• `IdleTimeout`

• http.ListenAndServe
• Middleware
• HTTP client
• httptest

• 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