1. How I built my first web
app in Go
16 Sep 2014
Audrey Lim
audreylh@gmail.com
Twitter: @AudreyLim77

2. About Me
Building Go applications

3. About Me
Lawyer (1-2 yrs)

4. About Me
Lawyer (1-2 yrs)
Learning Journey
May – Jul 2014: HTML, CSS, JS

5. About Me
Lawyer (1-2 yrs)
Learning Journey
May – Jul 2014: HTML, CSS, JS
(codeacademy, books,
websites)

6. About Me
Lawyer (1-2 yrs)
Learning Journey
(codeacademy, books,
websites)
May – Jul 2014: HTML, CSS, JS
mid-Jul 2014: Go (1st backend)

7. About Me
Lawyer (1-2 yrs)
Learning Journey
(codeacademy, books,
websites)
(everywhere)
May – Jul 2014: HTML, CSS, JS
mid-Jul 2014: Go (1st backend)

8. About Me
Lawyer (1-2 yrs)
Learning Journey
(codeacademy, books,
websites)
(everywhere)
May – Jul 2014: HTML, CSS, JS
mid-Jul 2014: Go (1st backend)
mid-Aug 2014: deployed 1st app – CRUD app

9. About Me
Lawyer (1-2 yrs)
Learning Journey
(codeacademy, books,
websites)
(everywhere)
May – Jul 2014: HTML, CSS, JS
mid-Jul 2014: Go (1st backend)
mid-Aug 2014: deployed 1st app – CRUD app
end-Aug 2014: deployed 2nd app – API client

10. Go Resources
golang.org
Books and websites
Sample applications
Stackoverflow, Go-nuts mailing list

11. Go Resources
golang.org (Go Tour, Docs, Go blog)
Books and websites
Sample applications
Stackoverflow, Go-nuts mailing list

12. Go Resources
golang.org (Go Tour, Docs, Go blog)
Books and websites (www.golang-book.com, www.gobyexample.com)
Sample applications
Stackoverflow, Go-nuts mailing list

13. Go Resources
golang.org (Go Tour, Docs, Go blog)
Books and websites (www.golang-book.com, www.gobyexample.com)
Sample applications (Go Wiki, from books)
Stackoverflow, Go-nuts mailing list

14. Experience with Go

15. Building Go applications

16. CRUD App
Simple CRUD App using MySQL
for data persistence
API Client
Flickr, Weather API

17. 1st app: CRUD App
Sign up/Sign in
Read Status
Create Status
Delete Status
Edit Status
Sign out
MySQL

18. Basic Structure
package main
Import (
“fmt”
“net/http”
)
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprint(w, “hello world!”)
}
func main() {
http.HandleFunc(“/”, handler)
http.ListenAndServe(“:8080”, nil)
}

19. Basic Structure
package main
Import (
“fmt”
“net/http”
)
All executable commands use package main
Print output to client
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprint(w, “hello world!”)
}
func main() {
Handler function when root is
requested
http.HandleFunc(“/”, handler)
http.ListenAndServe(“:8080”, nil)
}
Local server connection
Go’s stdlib
Entry point

20. Libraries
import (
"database/sql"
"html/template"
"fmt"
"log"
"net/http"
"os"
_ "github.com/go-sql-driver/mysql"
"github.com/gorilla/mux"
"github.com/gorilla/securecookie”
)

21. Libraries
Standard library
import (
"database/sql"
"html/template"
"fmt"
"log"
"net/http"
"os"
_ "github.com/go-sql-driver/mysql"
"github.com/gorilla/mux"
"github.com/gorilla/securecookie”
)
External packages

22. Data Structs
Type Slice of Pointers to Post struct
type User struct {
Userid int64
Username string
Password string
Posts []*Post
}
type Post struct {
Tweetid string
Username string
Status string
}

23. Database functions
func ReadStatus() (res [][]string) { Return slice of slice of strings
err := db.Ping()
if err != nil {
log.Fatal(err)
}
rows, err := db.Query("SELECT id, tweet, username FROM posts WHERE
username = ? ORDER BY id DESC", currentuser)
if err != nil {
log.Fatal(err)
}
defer rows.Close()
var tweet, id, username string
for rows.Next() {
err := rows.Scan(&id, &tweet, &username)
if err != nil {
return res
}
var a []string
a = append(a, id, tweet, username)
res = append(res, a)
}
return
}

24. Database functions
func ReadStatus() (res [][]string) { Return slice of slice of strings
err := db.Ping()
if err != nil {
log.Fatal(err)
}
rows, err := db.Query("SELECT id, tweet, username FROM posts WHERE
username = ? ORDER BY id DESC", currentuser)
if err != nil {
log.Fatal(err)
}
defer rows.Close()
var tweet, id, username string
for rows.Next() {
err := rows.Scan(&id, &tweet, &username)
if err != nil {
return res
}
var a []string
a = append(a, id, tweet, username)
res = append(res, a)
}
return
}
Verify db connection
Raw queries
Append strings to slice
Append slice of strings to output

25. Handler functions
func homeHandler(w http.ResponseWriter, r *http.Request) {
Create slice with Post instances
Append slice of Post
instances to Posts slice
currentuser = getUserName(r)
if currentuser != "" {
var as []Post
a := User{}
m := ReadStatus()
for i := 0; i < len(m); i++ {
as = append(as, Post{Tweetid: m[i][0], Username:
currentuser, Status: m[i][1]})
}
a = User{Username: currentuser}
for i := 0; i < len(m); i++ {
a.Posts = append(a.Posts, &as[i])
}
renderTemplate(w, "home", "homepage", a)
} else {
http.Redirect(w, r, "/", 302)
}
}
Wrapper func around
html/template library

26. Func main
Open connection pool
Handlers for URL paths
func main() {
db, err = sql.Open("mysql",
os.Getenv("DB_USERNAME")+":"+os.Getenv("DB_PASSWORD")+"@tcp("+os.Getenv("DB
_CLEARDB")+":3306)/"+os.Getenv("DB_NAME"))
if err != nil {
log.Fatal(err)
}
defer db.Close()
router.HandleFunc("/", logHandler)
router.HandleFunc("/login", loginHandler)
router.HandleFunc("/home", homeHandler)
router.HandleFunc("/home/tweets", usertweetHandler).Methods("POST")
router.HandleFunc("/logout", logoutHandler).Methods("POST")
router.HandleFunc("/home/delete", deleteHandler).Methods("POST")
router.HandleFunc("/home/edit", editHandler).Methods("POST")
router.HandleFunc("/home/save", saveHandler).Methods("POST”)
router.PathPrefix("/").Handler(http.FileServer(http.Dir("./layout/")))
http.Handle("/", router)
err := http.ListenAndServe(":"+os.Getenv("PORT"), nil)
if err != nil {
panic(err)
}
}
Port for server
connection

27. 2nd app: API Client
Get a series of photos from Flickr
for a random city and display
current weather data for the same
city

28. Libraries
import (
"encoding/json"
"fmt"
"html/template"
"io/ioutil"
"log"
"math/rand"
"net/http"
"os"
"strconv"
"time"
)

29. Thank you.
https://github.com/AudreyLim/weathergo
https://github.com/AudreyLim/twittergo
audreylh@gmail.com
Twitter: @AudreyLim77