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DESCRIPTION
An introduction to the go programming language, emphasizing concurrency.
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Go ahead, make my day.
Intro to Go programming language
Me @torkale h8p://github.com/torkale torkale[at]gmail
Why Go?
Challenge
Safety & Performance Expressiveness
& Convenience
AL
Mascot Performance Type safety Concurrency Scalability ProducKvity
Respected Parents
Ken Thompson Unix, B, UTF-‐8, Plan 9 Rob Pike Plan 9, UTF-‐8, Limbo, Unix team The Unix Programming Environment The PracKce of Programming
History
Start Late 2007
Public 2009
Go 1.0 March 2012
Go 1.1 May 2013
Rob Pike Ken Thompson
Robert Griesmer
Hello
package main import "fmt" func greet() {
fmt.Println("Hello, I love you, won’t you tell me your name?”) } func main() {
greet() }
Web Server package main import ( "fmt" "net/h8p" ) func handler(w h8p.ResponseWriter, r *h8p.Request) { fmt.Fprine(w, ”Request from %s", r.URL.Path[1:]) } func main() { h8p.HandleFunc("/", handler) h8p.ListenAndServe(":8080", nil) }
BASICS
Basic types DeclaraKons CondiKons Loops Slice Map
Basic Types bool string int int8 int16 int32 int64 uint uint8 uint16 uint32 uint64 uintptr byte // alias for uint8 rune // alias for int32 // represents a Unicode code point float32 float64 complex64 complex128
DeclaraKons var i int i = getInteger() j := getInteger() value, err := getValueOrError() value2, _ := getValueOrError()
CondiKons var even bool if x%2 == 0 { even = true } if x%2 == 0 { even = true } else { even = false } if mod := x%2; mod == 0 { even = true }
Loops factorial := 1 for i := 2; i <= num; i++ { factorial *= i } nextPowerOf2 := 1 for nextPowerOf2 < num { nextPowerOf2 *=2 } for { // Forever }
Slice primes := []int{2, 3, 5, 7, 11, 13} fmt.Println("primes[1:4] ==", primes[1:4]) zeroes := make([]int, 5) fmt.Println("zeroes ==", zeroes) for i, v := range primes { fmt.Prine("(%d) = %d\n", i, v) } for _, v := range primes { fmt.Prine("%d\n", v) }
Map m := make(map[string]int) m["Ten"] = 10 fmt.Println(m) capitals := map[string]string{ "Jerusalem": "Israel", "Paris": "France", "London": "UK", } fmt.Println(capitals) delete(capitals, "London") v, present := capitals["London"] fmt.Println("The capital:", v, "Present?", present)
TYPES
Custom types Extension via composiKon Methods
Custom Types type Name string type Person struct { first Name last Name } type Hero struct { Person power string } type Crowd struct { people []Person }
Methods func (dude Person) FullName() string { return fmt.Sprine("%s %s", dude.first, dude.last) } func (dude Person) SetFirst(name Name) { dude.first = name } func (h *Hero) ToString() string { return fmt.Sprine("Name: %s Power: %s", h.FullName(), h.power) } func NewPerson(f, l Name) Person { return Person{f, l} }
INTERFACES
AbstracKon Duck typing Signatures Implicit
interfaces type Talker interface { Talk() string } func (dude Person) Talk() string { return fmt.Sprine("My name is %s", dude.FullName()) } func MakeSomeoneTalk(talker Talker) string { return talker.Talk() } func interfaces() { fmt.Println(MakeSomeoneTalk(NewPerson("Robert", "de Niro"))) }
FUNCTIONS
Higher-‐order funcKons Custom funcKon types Closures MulKple return values
FuncKons type PersonAcKon func(some Person) Name func (crowd Crowd) ConcatPersonAcKons(acKon PersonAcKon) string { var result string for _, dude := range crowd.people { result = fmt.Sprine("%s %s", result, acKon(dude)) } return result } func AllLastNames(crowd Crowd) string { return crowd.ConcatPersonAcKons(func(dude Person) Name { return dude.last }) }
defer func MeasureStart(label string) (string, Kme.Time) { return label, Kme.Now() } func Measure(label string, startTime Kme.Time) { duraKon := Kme.Now().Sub(startTime) fmt.Println(label, "ComputaKon took", duraKon) } func benchmark() { defer Measure(MeasureStart("benchmark()")) Kme.Sleep(Kme.Second) }
CONCURRENCY
CSP go-‐rouKne channels select
CommunicaKng SequenKal Processes
“Do not communicate by sharing memory; instead share memory by communicaKng”
go rouKnes var a string func Init() { a = "finally started" return } func doSomethingElse() { // … } func Simple() string{ go Init() doSomethingElse() return a }
tradiKonal var ( a string wg sync.WaitGroup ) func Init() { defer wg.Done() a = "finally started" } func Simple() string{ wg.Add(1) go Init() wg.Wait() // do something else return a }
channel package channel var ( a string ready chan bool ) func Init() { a = "finally started" ready <-‐ true } func Simple() string{ ready = make(chan bool) go Init() // do something else <-‐ready return a }
Producer / Consumer func producer(c chan string){ defer close(c) for { work := getWork() c <-‐ work } } func consumer(c chan string) { for msg := range c { process(msg) } } func ProducerConsumer() { c := make(chan string) go producer(c) consumer(c) }
Producer / Consumer func producer(c chan string){ defer close(c) for { work := getWork() c <-‐ work } } func consumer(c chan string, abort <-‐chan Kme.Time) { for { select { case msg := <-‐c: process(msg) case <-‐ abort: return } } } func ProducerConsumer() { c := make(chan string) go producer(c) abort := Kme.A|er(2*Kme.Second) consumer(c, abort) }
Barber Shop Var seats = make(chan Customer, 2) customers := []Customer{ "Al", "Bob", "Chad", "Dave" } ) func barber() { for { c := <-‐seats fmt.Println("Barber shaving", c) } } func (c Customer) enter() { select { case seats <-‐ c: default: fmt.Println("Customer", c, "Leaves") } } func BarberShop() { go barber() for _, c := range customers { go c.enter() } }
GO COMMAND
version build test get
install fmt … build -‐-‐race (1.1+)
h8p://golang.org/ h8p://tour.golang.org/ h8ps://code.google.com/p/go-‐wiki/wiki/Projects h8ps://groups.google.com/forum/#!forum/golang-‐nuts #go-‐nuts on irc.freenode.net h8ps://www.facebook.com/groups/golanggonuts
