jdd2014: go! the one language you have to try in 2014 - andrzej grzesik
Post on 01-Jul-2015
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golangthe one language you have to try in 2014
golangthe one language you have to try in 2014
about:me
dev going deeper
disclaimers
my opinions are my own
I hate computers
questions?shoot!
golang
gopher
free and open source
BSD licensed
comes from G
FASTand I mean FAST
tl;dr;C++ and ruby had a wild time
play with it tonight
so, why do I like go?
no runtime dependencies!
more pleasant than C
go toolchain
go command
most important thing
there is only one formatting
package main!!
import "fmt"!!
func main() {!!fmt.Println("Hello world")!}!
types
types• uint8, uint16, uint32, uint64
• int8, int16, int32, int64
• float32, float64
• complex64, complex128
• byte alias for uint8
• rune alias for int32
• string
func program() {! var text! text = “zomg"! more := "zomg"!!
fmt.Println(len(text));!}!
maps
func main() {! attendees := map[string]bool{! "Phil": true,! "Marcin": true,! }!!
fmt.Println(attendees["Phil"]) // true! fmt.Println(attendees["ags"]) // false! partygoers["ags"] = true! fmt.Println(attendees["ags"]) // true!}!
structs
type Rectangle struct {! a, b int32!}!!
func main() {! var rect Rectangle! rect = Rectangle{5, 10}! rect = Rectangle{a: 10, b: 5}!!
HasArea(s).Area()!}
type Square struct {! side int32!}!!
func (sq Square) Area() int32 {! return sq.side * sq.side!}!!
func main() {! s := Square{16}! area := s.Area()!}
interfaces
type Square struct {! side int32!}!!
func (sq Square) Area() int32 {! return sq.side * sq.side!}!!
type HasArea interface {! Area() int32!}!!
func main() {! s := Square{16}! HasArea(s).Area()!}
goroutineslightweight threads
func f(i int) {! amt := rand.Intn(1000)! time.Sleep(time.Duration(amt) * time.Millisecond)! fmt.Println(i)!}!!
func main() {! for i := 0; i < 3; i++ {! go f(i)! }! var input string! fmt.Scanln(&input)!}
how many will run? runtime.GOMAXPROCS(4)
channels
channels
• communicate between funcs
• typed
• thread-safe
channelschannel := make(chan int)!
unbuffered channels
• sync
• will wait when empty
buffered channelschannel := make(chan int, size)!
buffered channels
• async
• return 0 element when empty
• will only wait when full
basicschannel := make(chan int)!c <- a!!
<- c!!
a = <- c!!
a, ok = <- c!
func program() {! channel := make(chan int) !}!!
func from(connection chan int) {! connection <- rand.Intn(255)!}!!
func to(connection chan int) {! i := <- connection! fmt.Println(“much received", i)!}!
but that’s not cool yet
coordinate routines
func program() {! channel := make(chan int) !!
go func() {! close(channel)! // or! channel <- anything! }()!!
<- channel!}!
func program() {! latch := make(chan int) !!
go worker()! close(latch)!}!!
func worker() {! <- latch !}!
generators
id := make(chan int64)! go func() {! var counter int64 = 0! for {! id <- counter! counter += 1! } !}()
multiple channels at once!
func program() {! select {! case a := <- channel!!
case b, mkay := other!!
case output <- z!!
default:! }!}!
ranges
func fillIn(channel chan int) {! channel <- 1! channel <- 2! channel <- 4! close(channel)!}!!
func main() {! channel := make(chan int)! go fillIn(channel)!!
for s := range channel {! fmt.Printf("%d \n", s)! }!}
packages
[18:48][agrzesik@melmac:~/vcs/talks/go/hello]!$ find .!.!./bin!./bin/main!./pkg!./pkg/darwin_amd64!./pkg/darwin_amd64/hello.a!./src!./src/hello!./src/hello/hello.go!./src/main!./src/main/.main.go.swp!./src/main/main.go!
import (! "code.google.com/p/go.net/websocket"! "fmt"! "net/http"!)!
go get
net
echo server
const listenAddr = "localhost:4000"!!
func main() {! l, err := net.Listen("tcp", listenAddr)! if err != nil {! log.Fatal(err)! }! for {! c, err := l.Accept()! if err != nil {! log.Fatal(err)! }! io.Copy(c, c)! }!}
concurrent echo server
const listenAddr = "localhost:4000"!!
func main() {! l, err := net.Listen("tcp", listenAddr)! if err != nil {! log.Fatal(err)! }! for {! c, err := l.Accept()! if err != nil {! log.Fatal(err)! }! go io.Copy(c, c)! }!}
const listenAddr = "localhost:4000"!!
func main() {! l, err := net.Listen("tcp", listenAddr)! if err != nil {! log.Fatal(err)! }! for {! c, err := l.Accept()! if err != nil {! log.Fatal(err)! }! io.Copy(c, c)! }!}
websockets?
func main() {! http.Handle("/", websocket.Handler(handler))! http.ListenAndServe("localhost:1984", nil)!}!!
func handler(c *websocket.Conn) {! var s string! fmt.Fscan(c, &s)! fmt.Println("Received:", s)! fmt.Fprint(c, “hey!”)!}!
so, what looks bad?
type AssetMetas struct {!!Metas []AssetMeta `json:"assetMetas"`! }!!
type AssetMeta struct {!!ResourceName string `json:"resource_name"`! !Md5 string `json:"md5"`! !Urls []string `json:"urls"`! }!
so, go code!
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