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Developing Web Apps with Go Chang Sau Sheong Sep 2014

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What are   Web applications?

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How does web applications work?

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Browser/Client Server

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Browser/Client Server HTTP Request

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Browser/Client Server HTTP Request • Request line GET /some/index.html HTTP/1.1

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Browser/Client Server HTTP Request • Request line GET /some/index.html HTTP/1.1 • Request headers

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Browser/Client Server HTTP Request • Request line GET /some/index.html HTTP/1.1 • Request headers • Empty line

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Browser/Client Server HTTP Request • Request line GET /some/index.html HTTP/1.1 • Request headers • Empty line • Message body (optional)

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Browser/Client Server HTTP Request HTTP Response • Request line GET /some/index.html HTTP/1.1 • Request headers • Empty line • Message body (optional)

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Browser/Client Server HTTP Request HTTP Response • Request line GET /some/index.html HTTP/1.1 • Request headers • Empty line • Message body (optional) • Status line HTTP/1.1 200 OK

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Browser/Client Server HTTP Request HTTP Response • Request line GET /some/index.html HTTP/1.1 • Request headers • Empty line • Message body (optional) • Status line HTTP/1.1 200 OK • Response headers

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Server

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Server HTTP Request

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Server HTTP Request 1.Process request

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Server HTTP Request 1.Process request 2.Execute application logic

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Server HTTP Request 1.Process request 2.Execute application logic 3.Generate response

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Server HTTP Request HTTP Response 1.Process request 2.Execute application logic 3.Generate response

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Parts of a web app • Routes  Processing the request • Templates  Generating response • Store  Persisting data

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What does Go have?

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net/http

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net/http 10

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net/http • Server -‐ ServeMux(type), Handler(type), Handle(func), HandleFunc(func), ListenAndServe(func), Serve(func) 10

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net/http • Server -‐ ServeMux(type), Handler(type), Handle(func), HandleFunc(func), ListenAndServe(func), Serve(func) • Client -‐ Get, Post, Head etc (func) 10

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net/http • Server -‐ ServeMux(type), Handler(type), Handle(func), HandleFunc(func), ListenAndServe(func), Serve(func) • Client -‐ Get, Post, Head etc (func) • Request, Response, ResponseWriter (type) 10

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html/template

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Routes Process the request

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Routes package main! ! import (! "fmt"! "net/http"! )! ! func handler(w http.ResponseWriter, r *http.Request) {! fmt.Fprintf(w, "Hello World, %s!", r.URL.Path[1:])! }! ! func main() {! http.HandleFunc("/", handler)! http.ListenAndServe(":8080", nil)! }!

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Routes package main! ! import (! "fmt"! "net/http"! )! ! func main() {! mux := http.NewServeMux()! mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {! fmt.Fprintf(w, "Hello World, %s!", r.URL.Path[1:])! })! http.ListenAndServe(":8080", mux)! }!

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Routes package main! ! import (! "fmt"! "net/http"! )! ! type MyHandler struct {}! ! func (h *MyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {! fmt.Fprintf(w, "Hello World, %s!", r.URL.Path[1:])! }! ! func main() {! http.ListenAndServe(":8080", &MyHandler{})! }!

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Routes type MyHandler struct {}! ! func (h *MyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {! fmt.Fprintf(w, "Hello World, %s!", r.URL.Path[1:])! }! ! func main() {! server := &http.Server{! ! Addr: "0.0.0.0:8080",! ! Handler: &MyHandler{},! ! ReadTimeout: 10 * time.Second,! ! WriteTimeout: 600 * time.Second,! ! MaxHeaderBytes: 1 << 20,! }! server.ListenAndServe() ! }

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Routes package main! ! import (! "fmt"! "net/http"! "github.com/julienschmidt/httprouter"! )! ! func main() {! router := httprouter.New() ! router.GET("/:name", hello) ! http.ListenAndServe(":8080", router)! }! ! func hello(w http.ResponseWriter, r *http.Request, p httprouter.Params) {! fmt.Fprintf(w, "Hello World, %s!", p.ByName("name"))! }!

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Static assets? • Images • Stylesheets (CSS) • Javascript • Fonts

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Serve Files func main() {! router := httprouter.New() ! router.ServeFiles("/images/*filepath", ! http.Dir("public/images"))! router.ServeFiles("/css/*filepath", ! http.Dir("public/css"))! router.ServeFiles(“/fonts/*filepath",! http.Dir("public/fonts"))! router.ServeFiles("/js/*filepath", ! http.Dir("public/js"))! http.ListenAndServe(":8080", router)! }! !

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Templates Generate the response

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Templates 21 Hello World! This is { name } name = “Sau Sheong” Hello World! This is Sau Sheong +

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Templates

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Templates • text/template -‐ data driven templates

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Templates • text/template -‐ data driven templates • html/template -‐ data driven templates for HTML

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Templates • text/template -‐ data driven templates • html/template -‐ data driven templates for HTML • Actions (data evaluations or control structure) -‐ delimited by {{ and }}

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Templates • text/template -‐ data driven templates • html/template -‐ data driven templates for HTML • Actions (data evaluations or control structure) -‐ delimited by {{ and }} • Arguments -‐ values/variables in the template • Pass variables to template, accessible through the ‘dot’ {{ . }}

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Templates

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Templates • Pipeline -‐ a chained sequence of commands

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Templates • Pipeline -‐ a chained sequence of commands • Function -‐ global functions (predefined) or custom functions

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Templates • Pipeline -‐ a chained sequence of commands • Function -‐ global functions (predefined) or custom functions • Include other templates with keyword ‘template’

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Generating response

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Generating response 1. Set {{ define }} in the template

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Generating response 1. Set {{ define }} in the template 2. Allocate the template (in the route) using New()

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Generating response 1. Set {{ define }} in the template 2. Allocate the template (in the route) using New() 3. Create the template by parsing one or more files using Parse(), ParseFiles() or ParseGlob()

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t1.html 25 {{ define "t1" }}! ! ! ! {{ template "header" }}! ! Hello World, {{ . }}!! ! ! ! {{ end }}!

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header.html 26 {{ define "header" }}! ! ! Template Example! ! {{ end }}!

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templates.go 27 package main! ! import (! "os"! "html/template"! )! ! func main() {! t := template.New("t1")! t = template.Must(t.ParseGlob("*.html")) ! t.Execute(writer, "Sau Sheong")! }!

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templates.go 27 package main! ! import (! "os"! "html/template"! )! ! func main() {! t := template.New("t1")! t = template.Must(t.ParseGlob("*.html")) ! t.Execute(writer, "Sau Sheong")! }! Allocate

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templates.go 27 package main! ! import (! "os"! "html/template"! )! ! func main() {! t := template.New("t1")! t = template.Must(t.ParseGlob("*.html")) ! t.Execute(writer, "Sau Sheong")! }! Create

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templates.go 27 package main! ! import (! "os"! "html/template"! )! ! func main() {! t := template.New("t1")! t = template.Must(t.ParseGlob("*.html")) ! t.Execute(writer, "Sau Sheong")! }! Execute

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templates.go 27 package main! ! import (! "os"! "html/template"! )! ! func main() {! t := template.New("t1")! t = template.Must(t.ParseGlob("*.html")) ! t.Execute(writer, "Sau Sheong")! }!

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Response 28 ! ! ! ! ! Template Example! ! ! ! Hello World, Sau Sheong!! !

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Response 28 ! ! ! ! ! Template Example! ! ! ! Hello World, Sau Sheong!! ! from header.html

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Response 28 ! ! ! ! ! Template Example! ! ! ! Hello World, Sau Sheong!! ! from header.html replaces {{ . }}

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templates.go 29 type Presentation struct {! Title string! Author string! }! ! func main() {! t := template.New("t2")! t = template.Must(t.ParseGlob("*.html")) ! presso := Presentation{! Title: "Write Web Applications with Go",! Author: "Chang Sau Sheong",! }! t.Execute(writer, presso)! }!

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t2.html 30 {{ define "t2" }}! ! ! ! {{ template "header" }}! !

! ! ! ! {{ end }}!

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Response 31 ! ! ! ! ! Template Example! ! ! !

Write Web Applications with Go

Chang Sau Sheong

! ! !

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Store Persist application data

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SQL

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SQL • Direct SQL statements

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SQL • Direct SQL statements • Mappers (ORMs)

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SQL • Direct SQL statements • Mappers (ORMs) • gorp

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SQL • Direct SQL statements • Mappers (ORMs) • gorp • hood

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SQL • Direct SQL statements • Mappers (ORMs) • gorp • hood • beego orm

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SQL • Direct SQL statements • Mappers (ORMs) • gorp • hood • beego orm • gorm

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database/sql

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35 package main! ! import(! "log"! "fmt" ! "database/sql"! _ "github.com/lib/pq"! )! ! func main() {! db, _ := sql.Open("postgres", "dbname=blog sslmode=disable”)! defer db.Close() ! ! rows, err := db.Query("SELECT name, email FROM users WHERE email = $1", “[email protected]”); if err != nil {! log.Fatal(err)! }! for rows.Next() {! var name, email string! if err := rows.Scan(&name, &email); err != nil {! log.Fatal(err)! }! fmt.Printf("%s - %s\n", name, email)! }! }!

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Ok when small codebase

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Ok when small codebase Painful otherwise

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37 https://github.com/jinzhu/gorm

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37 https://github.com/jinzhu/gorm This is NOT part of standard Go libraries

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Define models 38 type User struct {! Id int64! Uuid string `sql:"size:255;not null;unique"`! Email string `sql:"size:255"`! Password string `sql:"size:255"`! Name string `sql:"size:255"`! CreatedAt time.Time! }! ! type Session struct {! Id int64! Uuid string `sql:"size:255;not null;unique"`! UserId int64 ! CreatedAt time.Time! } // foreign key for User table

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Initialize database 39 var DB gorm.DB! ! // initialize gorm! func init() {! var err error! DB, err = gorm.Open("postgres", "user=test password=test dbname=test sslmode=disable")! if err != nil {! panic(fmt.Sprintf("Got error when connect database, the error is '%v'", err))! }! migrate()! }

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Migrate tables 40 // Create tables! func migrate() {! DB.Exec("DROP TABLE users;DROP TABLE sessions;")! DB.AutoMigrate(User{})! DB.AutoMigrate(Session{})! }

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Create 41 user := User{Name: "Sau Sheong", ! Email: "[email protected]", ! Password: “passw0rd”,! }! DB.Save(&user) ! !

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Query 42 var user = User{}! // Get the first record! err := DB.Where("email = ?", ! "[email protected]").First(&user).Error! if err != nil {! fmt.Println("Cannot retrieve this user:", err)! } ! ! // Get the multiple records! var users []User! err := DB.Where("email LIKE ?", ! "%@gmail.com").Find(&users).Error! if err != nil {! fmt.Println("Cannot retrieve users:", err)! }

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Update & Delete 43 var user = User{}! // Get the first record! err := DB.Where("email = ?", ! "[email protected]").First(&user).Error! if err != nil {! fmt.Println("Cannot retrieve this user:", err)! } ! ! // Update the name! user.Name = "Batman"! DB.Save(&user)! ! // Delete the record! DB.Delete(&user)!

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Callbacks 44 // Before creating a user, add in the uuid! func (u *User) BeforeCreate() (err error) {! ! ! u.Password = encrypt(u.Password)! ! u.Uuid = createUUID()! ! return! }

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Associations 45 user := User{Name: "Sau Sheong", ! Email: "[email protected]", ! Password: "test",! }! DB.Save(&user) ! ! sess := Session{UserId: user.Id}! DB.Save(&sess)! ! var usr User! err := DB.Model(&sess).Related(&usr).Error! if err != nil {! fmt.Println("Cannot retrieve this user:", err)! } ! ! var session Session! err := DB.Model(&user).Related(&session).Error! if err != nil {! fmt.Println("Cannot retrieve this session:", err)! }

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Other features

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Other features • Query chains

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Other features • Query chains • Batch updates and deletes

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Other features • Query chains • Batch updates and deletes • Soft delete

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Other features • Query chains • Batch updates and deletes • Soft delete • Associations

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Other features • Query chains • Batch updates and deletes • Soft delete • Associations • Has One

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Other features • Query chains • Batch updates and deletes • Soft delete • Associations • Has One • Belongs To

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Other features • Query chains • Batch updates and deletes • Soft delete • Associations • Has One • Belongs To • Has Many

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Other features • Query chains • Batch updates and deletes • Soft delete • Associations • Has One • Belongs To • Has Many • Many to Many

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Other features

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Other features • FirstOrInit, FirstOrCreate

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Other features • FirstOrInit, FirstOrCreate • Order, Limit, Offset, Count

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Other features • FirstOrInit, FirstOrCreate • Order, Limit, Offset, Count • Group, Having, Joins

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Other features • FirstOrInit, FirstOrCreate • Order, Limit, Offset, Count • Group, Having, Joins • Transactions

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Other features • FirstOrInit, FirstOrCreate • Order, Limit, Offset, Count • Group, Having, Joins • Transactions • Logger

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Frameworks • Gorilla web toolkit • Martini • Gin Gonic • Beego • Revel

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Testing Testing Go Web Apps

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Testing is built-in

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**_test.go

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func TestXXX(t *testing.T) { }

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func TestXXX(t *testing.T) { } // Some test code

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> go build

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> go build Compile Go code

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> go build > go test Compile Go code

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> go build > go test Compile Go code Run tests on Go code

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testing net/http/httptest

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testing net/http/httptest Generic testing library

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testing net/http/httptest Generic testing library Testing library for web applications

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Unit Testing 55 package main! ! import( ! "testing"! )! ! // Test package function that adds a new user! func TestAddUser(t *testing.T) {! addUser("Sau Sheong", "[email protected]", "password")! if val, ok := users["[email protected]"]; !ok {! t.Errorf("Cannot add user")! } else {! if val.Name != "Sau Sheong" {! t.Errorf("User name is wrong")! }! }! }

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HTTP Testing 56 package main! ! ...! ! func TestIndex(t *testing.T) { ! router := httprouter.New()! router.GET("/", index)! writer := httptest.NewRecorder()! request, _ := http.NewRequest("GET", "/", nil) ! router.ServeHTTP(writer, request)! ! if writer.Code != 302 {! t.Errorf("Response code is %v", writer.Code)! } ! }

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HTTP Testing 57 func TestSignUp(t *testing.T) {! router := httprouter.New()! router.POST("/signup", createUser)! writer := httptest.NewRecorder()! body := strings.NewReader("name=Sau Sheong&[email protected]&password=password")! request, _ := http.NewRequest("POST", "/signup", body)! request.Header.Add("Content-Type", "application/x-www- form-urlencoded")! router.ServeHTTP(writer, request)! ! if writer.Code != 302 {! t.Errorf("Response code is %v", writer.Code)! }! if writer.Header().Get("Location") != "/login" {! t.Errorf("Location is %v", writer.Header().Get("Location"))! }! }

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HTTP Testing 58 func TestAuthenticate(t *testing.T) {! addUser("Sau Sheong", "[email protected]", "password")! router := httprouter.New()! router.POST("/login", authenticate) ! writer := httptest.NewRecorder()! body := strings.NewReader("[email protected]&password=pa ssword")! request, _ := http.NewRequest("POST", "/login", body)! request.Header.Add("Content-Type", "application/x-www- form-urlencoded")! router.ServeHTTP(writer, request)! ...! if !strings.HasPrefix(writer.Header().Get("Set- Cookie"), "pixelate_cookie") {! t.Errorf("Cookie not set")! }! }

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Go on the Cloud Deploying to Google App Engine

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Go App Engine 60

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Go App Engine • Download the Go App Engine SDK 60

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Go App Engine • Download the Go App Engine SDK • Install Mercurial 60

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Go App Engine • Download the Go App Engine SDK • Install Mercurial • Add a file app.yaml to the same directory 60

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Go App Engine • Download the Go App Engine SDK • Install Mercurial • Add a file app.yaml to the same directory 60 application: pixelate! version: 1! runtime: go! api_version: go1! ! handlers:! - url: /.*! script: _go_app

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Go App Engine 61

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Go App Engine • Code changes required: 61

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Go App Engine • Code changes required: • Change all package names from main to the application name (in this case it is sausheong-pixelate) 61

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Go App Engine • Code changes required: • Change all package names from main to the application name (in this case it is sausheong-pixelate) • Change the main() function to init() 61

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Go App Engine • Code changes required: • Change all package names from main to the application name (in this case it is sausheong-pixelate) • Change the main() function to init() • Change from http.ListenAndServe() to http.Handle(mux) 61

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Run locally 62

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Run locally • Run at command line: 62

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Run locally • Run at command line: 62 go_appengine/dev_appserver.py sausheong-pixelate

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Run locally • Run at command line: • Open browser to: 62 go_appengine/dev_appserver.py sausheong-pixelate

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Run locally • Run at command line: • Open browser to: 62 go_appengine/dev_appserver.py sausheong-pixelate http://localhost:8080

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Deploy to Google App Engine 63

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Deploy to Google App Engine • Create app on Google App Engine 63

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Deploy to Google App Engine • Create app on Google App Engine • Run at command line: 63 go_appengine/goapp deploy sausheong-pixelate

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Deploy to Google App Engine • Create app on Google App Engine • Run at command line: 63 go_appengine/goapp deploy sausheong-pixelate

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Deploy to Google App Engine • Create app on Google App Engine • Run at command line: • Open browser to: 63 go_appengine/goapp deploy sausheong-pixelate

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Deploy to Google App Engine • Create app on Google App Engine • Run at command line: • Open browser to: 63 go_appengine/goapp deploy sausheong-pixelate http://sausheong-pixelate.appspot.com

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My projects 64 • Pixelate  Convert a JPEG file to a pixelated version • TodayReader  A faster, simpler Today (newspaper) reader • GoAuthServ  Simple authentication service • Polyglot  Multi-‐language web framework

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Thank you [email protected] [email protected] http://github.com/sausheong @sausheong