HTTP and Networking

Overview

Go’s net/http package provides a complete HTTP client and server implementation.

HTTP Client

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

body, _ := io.ReadAll(resp.Body)

Custom Request

req, _ := http.NewRequest("POST", url, bytes.NewBuffer(data))
req.Header.Set("Content-Type", "application/json")
req.Header.Set("Authorization", "Bearer "+token)

client := &http.Client{Timeout: 10 * time.Second}
resp, err := client.Do(req)

With Context

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

req, _ := http.NewRequestWithContext(ctx, "GET", url, nil)
resp, err := http.DefaultClient.Do(req)

HTTP Server

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, %s!", r.URL.Path[1:])
}

func main() {
    http.HandleFunc("/", handler)
    log.Fatal(http.ListenAndServe(":8080", nil))
}

JSON API

func userHandler(w http.ResponseWriter, r *http.Request) {
    user := User{Name: "Alice"}

    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(user)
}

Middleware

func logging(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        log.Printf("%s %s", r.Method, r.URL)
        next.ServeHTTP(w, r)
    })
}

http.Handle("/", logging(http.HandlerFunc(handler)))

ServeMux

mux := http.NewServeMux()
mux.HandleFunc("/users", usersHandler)
mux.HandleFunc("/posts", postsHandler)

http.ListenAndServe(":8080", mux)

Static Files

fs := http.FileServer(http.Dir("./static"))
http.Handle("/static/", http.StripPrefix("/static/", fs))

Summary

Function	Purpose
`http.Get()`	Simple GET request
`http.Post()`	Simple POST request
`http.NewRequest()`	Custom request
`http.HandleFunc()`	Register handler
`http.ListenAndServe()`	Start server