Examples Filter
package main

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

func main() {

	fileUrl := "https://golangcode.com/images/avatar.jpg"

	if err := DownloadFile("avatar.jpg", fileUrl); err != nil {
		panic(err)
	}
}

// DownloadFile will download a url to a local file. It's efficient because it will
// write as it downloads and not load the whole file into memory.
func DownloadFile(filepath string, url string) error {

	// Get the data
	resp, err := http.Get(url)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	// Create the file
	out, err := os.Create(filepath)
	if err != nil {
		return err
	}
	defer out.Close()

	// Write the body to file
	_, err = io.Copy(out, resp.Body)
	return err
}
Parsing a URL which includes a scheme, authentication info, host, port, path, query params, and a query fragment.
package main

import (
    "fmt"
    "net"
    "net/url"
)

func main() {

    s := "postgres://user:pass@host.com:5432/path?k=v#f"

    u, err := url.Parse(s)
    if err != nil {
        panic(err)
    }

    fmt.Println(u.Scheme)

    fmt.Println(u.User)
    fmt.Println(u.User.Username())
    p, _ := u.User.Password()
    fmt.Println(p)

    fmt.Println(u.Host)
    host, port, _ := net.SplitHostPort(u.Host)
    fmt.Println(host)
    fmt.Println(port)

    fmt.Println(u.Path)
    fmt.Println(u.Fragment)

    fmt.Println(u.RawQuery)
    m, _ := url.ParseQuery(u.RawQuery)
    fmt.Println(m)
    fmt.Println(m["k"][0])
}
The Go standard library comes with excellent support for HTTP clients and servers in the net/http package. In this example we’ll use it to issue simple HTTP requests.
package main

import (
    "bufio"
    "fmt"
    "net/http"
)

func main() {

    // Issue an HTTP GET request to a server.
    // http.Get is a convenient shortcut around creating an http.Client object and calling its Get method;
    // it uses the http.DefaultClient object which has useful default settings.
    resp, err := http.Get("http://gobyexample.com")
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()

    fmt.Println("Response status:", resp.Status)

    scanner := bufio.NewScanner(resp.Body)
    for i := 0; scanner.Scan() && i < 5; i++ {
        fmt.Println(scanner.Text())
    }

    if err := scanner.Err(); err != nil {
        panic(err)
    }
}
package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"strings"
)

func main() {

	resp, err := http.Post("https://mysite.com/endpoint", "text/plain", strings.NewReader("Content Body"))
	if err != nil {
		panic(err)
	}

	defer resp.Body.Close()
	fmt.Println(resp.Status)

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		panic(err)
	}
	fmt.Println(string(body))
}
Writing a basic HTTP server is easy using the net/http package.
package main

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

// A fundamental concept in net/http servers is handlers.
// A handler is an object implementing the http.Handler interface.
// A common way to write a handler is by using the http.HandlerFunc adapter on functions
// with the appropriate signature.
func hello(w http.ResponseWriter, req *http.Request) {

	// Functions serving as handlers take a http.ResponseWriter and a http.Request as arguments.
	// The response writer is used to fill in the HTTP response.
	// Here our simple response is just “hello\n”.
	fmt.Fprintf(w, "hello\n")
}

func headers(w http.ResponseWriter, req *http.Request) {

	// This handler does something a little more sophisticated by reading all the
	// HTTP request headers and echoing them into the response body.
	for name, headers := range req.Header {
		for _, h := range headers {
			fmt.Fprintf(w, "%v: %v\n", name, h)
		}
	}
}

func main() {

	// We register our handlers on server routes using the http.HandleFunc convenience function.
	// It sets up the default router in the net/http package and takes a function as an argument.
	http.HandleFunc("/hello", hello)
	http.HandleFunc("/headers", headers)

	// Finally, we call the ListenAndServe with the port and a handler.
	// nil tells it to use the default router we’ve just set up.
	log.Fatal(http.ListenAndServe(":8090", nil))
}
package main

import (
	"log"
	"net/smtp"
)

func main() {
	// Connect to the remote SMTP server.
	c, err := smtp.Dial("mail.example.com:25")
	if err != nil {
		log.Fatal(err)
	}
}
package main

import (
	"fmt"
	"net/http"

	"github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
}

func main() {
	http.HandleFunc("/echo", func(w http.ResponseWriter, r *http.Request) {
		conn, _ := upgrader.Upgrade(w, r, nil) // error ignored for sake of simplicity

		for {
			// Read message from browser
			msgType, msg, err := conn.ReadMessage()
			if err != nil {
				return
			}

			// Print the message to the console
			fmt.Printf("%s sent: %s\n", conn.RemoteAddr(), string(msg))

			// Write message back to browser
			if err = conn.WriteMessage(msgType, msg); err != nil {
				return
			}
		}
	})

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		http.ServeFile(w, r, "websockets.html")
	})

	http.ListenAndServe(":8080", nil)
}

/*





*/
package main

import (
	"fmt"
	"net/http"

	"github.com/gorilla/mux"
)

func main() {
	r := mux.NewRouter()

	// Methods
	// r.HandleFunc("/books/{title}", CreateBook).Methods("POST")
	// r.HandleFunc("/books/{title}", ReadBook).Methods("GET")
	// r.HandleFunc("/books/{title}", UpdateBook).Methods("PUT")
	// r.HandleFunc("/books/{title}", DeleteBook).Methods("DELETE")

	// Hostname and Subdomains
	// r.HandleFunc("/books/{title}", BookHandler).Host("www.mybookstore.com")

	// Schemes
	// r.HandleFunc("/secure", SecureHandler).Schemes("https")
	// r.HandleFunc("/insecure", InsecureHandler).Schemes("http")

	// Path Prefix and Subrouters
	// bookrouter := r.PathPrefix("/books").Subrouter()
	// bookrouter.HandleFunc("/", AllBooks)
	// bookrouter.HandleFunc("/{title}", GetBook)

	r.HandleFunc("/books/{title}/page/{page}", func(w http.ResponseWriter, r *http.Request) {
		vars := mux.Vars(r)
		title := vars["title"]
		page := vars["page"]

		fmt.Fprintf(w, "You've requested the book: %s on page %s\n", title, page)
	})

	http.ListenAndServe(":80", r)
}
package main

import "net/http"

func main() {
	fs := http.FileServer(http.Dir("assets/"))
	http.Handle("/static/", http.StripPrefix("/static/", fs))

	http.ListenAndServe(":8080", nil)
}
package main

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

func logging(f http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		log.Println(r.URL.Path)
		f(w, r)
	}
}

func foo(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintln(w, "foo")
}

func main() {
	http.HandleFunc("/foo", logging(foo))
	http.ListenAndServe(":8080", nil)
}
You may want to persist visitor data through cookies sent and received as cookies.
package main

import (
	"fmt"
	"net/http"

	"github.com/gorilla/sessions"
)

var (
	// key must be 16, 24 or 32 bytes long (AES-128, AES-192 or AES-256)
	key   = []byte("super-secret-key")
	store = sessions.NewCookieStore(key)
)

func secret(w http.ResponseWriter, r *http.Request) {
	session, _ := store.Get(r, "cookie-name")

	// Check if user is authenticated
	if auth, ok := session.Values["authenticated"].(bool); !ok || !auth {
		http.Error(w, "Forbidden", http.StatusForbidden)
		return
	}

	// Print secret message
	fmt.Fprintln(w, "The cake is a lie!")
}

func login(w http.ResponseWriter, r *http.Request) {
	session, _ := store.Get(r, "cookie-name")

	// Authentication goes here
	// ...

	// Set user as authenticated
	session.Values["authenticated"] = true
	session.Save(r, w)
}

func logout(w http.ResponseWriter, r *http.Request) {
	session, _ := store.Get(r, "cookie-name")

	// Revoke users authentication
	session.Values["authenticated"] = false
	session.Save(r, w)
}

func main() {
	http.HandleFunc("/secret", secret)
	http.HandleFunc("/login", login)
	http.HandleFunc("/logout", logout)

	http.ListenAndServe(":8080", nil)
}
package main

import (
	"encoding/json"
	"fmt"
	"net/http"
)

type User struct {
	Firstname string `json:"firstname"`
	Lastname  string `json:"lastname"`
	Age       int    `json:"age"`
}

func main() {
	http.HandleFunc("/decode", func(w http.ResponseWriter, r *http.Request) {
		var user User
		json.NewDecoder(r.Body).Decode(&user)

		fmt.Fprintf(w, "%s %s is %d years old!", user.Firstname, user.Lastname, user.Age)
	})

	http.ListenAndServe(":8080", nil)
}
package main

import (
	"encoding/json"
	"net/http"
)

type User struct {
	Firstname string `json:"firstname"`
	Lastname  string `json:"lastname"`
	Age       int    `json:"age"`
}

func main() {
	http.HandleFunc("/encode", func(w http.ResponseWriter, r *http.Request) {
		peter := User{
			Firstname: "John",
			Lastname:  "Doe",
			Age:       25,
		}

		json.NewEncoder(w).Encode(peter)
	})

	http.ListenAndServe(":8080", nil)
}

// $ go run json.go
// $ curl -s http://localhost:8080/encode
// {"firstname":"John","lastname":"Doe","age":25}
Escape HTML so that special characters don't render as HTML but as text in the browser.
package main

import (
	"fmt"
	"html"
)

func main() {

	unescaped := ``
	escaped := html.EscapeString(unescaped)
	fmt.Println(escaped)
}
Last Run  :
<script>alert(123);</script>