Something about Golang - Speaker Deck

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#golang

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Pascal C/Asm Perl Java Evolution of a software developer PaintGo

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A little bit of history… 2007 2009 2012 2013 2015 The beginning Open sourced 1.0 1.1 1.5

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Where used? https://github.com/golang/go/wiki/GoUsers Google, Docker, Heroku, Cloud Foundry, CoreOS, InﬂuxDB, Dropbox, OpenShift, SoundCloud, Toggl, etc. In the clouds!

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“Can't reach the pedals. no brakes. gaining speed. eyes bulging in horror. technical debt crash eminent. “ — Tim Dysinger, @dysinger

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Paul Phillips @extempore2 “go is a terrible, terrible language, yet still a major productivity boost. Amdahl's law in another context.” “You often see languages which are ﬁghting the last war. Go is ﬁghting the War of 1812.”

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“reduce: what you will do with your expectations after you start with Go” “Rust and Scala drown you in complexity. Go drowns you in simplicity.” Paul Phillips @extempore2

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Tour of Go tour.golang.org

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package main import "fmt" func main() { fmt.Println("Hello, Devclub!") }

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package main import "fmt" func main() { fmt.Println("Hello, Devclub!") } Java-developers reaction to the capital letter in a function name

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Missing stuﬀ No classes No generics No inheritance No method overriding No exceptions etc

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No generics? No exceptions? Wut!?

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Features Functions Structures Interfaces Methods Slices Pointers Go-routines Channels

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func main() { fmt.Println("1 + 2 =", add(1, 2)) } func add(a int, b int) int { return a + b } Functions

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func main() { fmt.Println("1 + 2 =", add(1, 2)) } func add(a int, b int) int { return a + b } Functions

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func main() { fmt.Println("1 + 2 =", add(1, 2)) } func add(a, b int) int { return a + b } Functions

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func main() { s, p := calculate(1, 2) fmt.Printf("1+2=%d, 1*2=%d", s, p) } func calculate(a, b int) (int, int) { return a + b, a * b } Functions

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func main() { s, p := calculate(1, 2) fmt.Printf("1+2=%d, 1*2=%d", s, p) } func calculate(a, b int) (int, int) { return a + b, a * b } Functions

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func main() { s, p := calculate(1, 2) fmt.Printf("1+2=%d, 1*2=%d", s, p) } func calculate(a, b int) (s, p int) { s := a + b p := a * b return } Functions

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func main() { double := func(a int) int { return a * 2 } double(14) } Functions as values

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func main() { double := factory() double(14) } func factory() func(a int) int { return func(a int) int { return a * 2 } } Functions as values

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Arrays var a [4]int a[0] = 1 i := a[0] http://blog.golang.org/go-slices-usage-and-internals arr := [2]string{"Foo", "Bar"} arr := […]string{"Foo", "Bar"}

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Slices a := []int{1, 2, 3} // [1 2 3] No size deﬁnition b := append(a, 4, 5) // [1 2 3 4 5] c := make(c, 3) // [0 0 0] d := b[1:3] // [2 3] e := b[:3] // [1 2 3]

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Maps monthdays := map[string]int{ "Jan": 31, "Feb": 28, "Mar": 31, "Apr": 30, "May": 31, "Jun": 30, "Jul": 31, "Aug": 31, "Sep": 30, "Oct": 31, "Nov": 30, "Dec": 31, } for month, days := range monthdays { fmt.Println(month, days) }

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Maps monthdays := map[string]int{ "Jan": 31, "Feb": 28, "Mar": 31, "Apr": 30, "May": 31, "Jun": 30, "Jul": 31, "Aug": 31, "Sep": 30, "Oct": 31, "Nov": 30, "Dec": 31, } value, ok := monthdays["Jan"]  fmt.Println(value) // 31 fmt.Println(ok) // true

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Pointers var p *int i := 42 p = &i fmt.Println(*p) *p = 21 fmt.Println(i) 42 21

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Pointers var p *int i := 42 p = &i fmt.Println(*p) *p = 21 fmt.Println(i)

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Pointers var p *int i := 42 p = &i fmt.Println(*p) *p = 21 fmt.Println(i) No pointer arithmetics

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Structures type Vertex struct { X int Y int }

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Structures type Vertex struct { X int Y int } func main() { fmt.Println(Vertex{1, 2}) }

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Methods type Vertex struct { X int Y int } func (v Vertex) Total() int { return v.X + v.Y }

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Methods type Vertex struct { X int Y int } func (v Vertex) Total() int { return v.X + v.Y } v := Vertex{1, 2} v.Total()

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Interfaces type Entity interface { Total() int }

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Interfaces type Entity interface { Total() int } Vertex implements Entity func (v Vertex) Total() int { return v.X + v.Y }

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Interfaces v := Vertex {1, 2} blah(v) func blah(e Entity) { e.Total() }

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Interfaces func foo(x interface{}) int { x.(Vertex).Total() }

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Interfaces func foo(x interface{}) int { x.(Vertex).Total() } panic: interface conversion: interface is main.Vertex2, not main.Vertex goroutine 1 [running]: main.main() main.go:25 +0xcd exit status 2 foo(Vertex2{1,2})

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A programmer had a problem. He thought to solve it with threads. two Now problems. he has

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Go-routines foo(Vertex2{1,2}) go foo(Vertex2{1,2}) Usual function call Function call in a go-routine

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func ready(w string, sec int) { time.Sleep(time.Duration(sec) * time.Second) fmt.Println(w, "is ready!") } func main() { go ready("Tea", 2) go ready("Coffee", 1) fmt.Println("I'm waiting") time.Sleep(5 * time.Second) } I’m waiting Coﬀee is ready Tea is ready

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Channels ci := make(chan int) cs := make(chan string) cf := make(chan interface{}) ci <- 1 ← send value 1 into channel ci i := <-ci ← read int from channel ci

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var c chan int func ready(w string, sec int) { time.Sleep(time.Duration(sec) * time.Second) fmt.Println(w, "is ready!”) с <-‐ 1 } func main() { go ready("Tea", 2) go ready("Coffee", 1) fmt.Println("I'm waiting") <-‐c <-‐c }

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var done = make(chan bool) var msgs = make(chan int) func produce() { for i := 0; i < 10; i++ { msgs <-‐ i } done <-‐ true } func consume() { for { msg := <-‐msgs println(msg) } } func main() { go produce() go consume() <-‐ done }

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Environment https://golang.org/doc/code.html#Workspaces

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Environment

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Environment

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Tooling • go (version, build, test, get, install, …) • gofmt • godoc • Editors (vim, atom, IntelliJ IDEA, Sublime Text)

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My choice

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What’s missing? Debugger IntelliJ IDEA plugin is still in development Can use GDB, but better do something else instead Dependency management A lot of diﬀerent solutions, no de facto standard -vendor option in 1.5

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Cross-compilation http://dave.cheney.net/2015/03/03/cross-compilation-just-got- a-whole-lot-better-in-go-1-5 env GOOS=linux GOARCH=386 go build hello.go 1. Build on Mac for Linux 2. Run the binary without installing extra dependencies or runtime on Linux host

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Testing package math func Add(a, b int) int { return a + b } package math import "testing" func TestAdd(t *testing.T){ if Add(1, 3) != 4 { t.Error("Expecting 4") } }

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Testing package math func Add(a, b int) int { return a + b } package math import "testing" func TestAdd(t *testing.T){ if Add(1, 3) != 4 { t.Error("Expecting 4") } } /usr/local/go/bin/go test -‐v ./... -‐run ^TestAdd$ Testing started at 03:35 ... ? _/Users/anton/work-‐src/mygo [no test files]PASS ok _/Users/anton/work-‐src/mygo/math 0.007s

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Q: Can you build the enterprise apps in Go? And now a million $$ question https://www.youtube.com/watch?v=cFJkLfujOts Building bank in Go: A: Apparently, you can :)

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Can I haz decimal type? https://github.com/shopspring/decimal import "github.com/shopspring/decimal" … x, _ := decimal.NewFromString("0.1")  sum := x.Add(x).Add(x) // 0.3

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import ( "net/http" "fmt" ) func handler(w http.ResponseWriter, r *http.Request) { fmt.Fprintf(w, "Welcome!") } func main() { http.HandleFunc("/", handler) http.ListenAndServe(":8080", nil) } Compare to Java?

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Frameworks Gorilla web toolkit http://www.gorillatoolkit.org/ Go-Kit http://gokit.io List of various frameworks and libraries: https://github.com/avelino/awesome-go

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Resources http://www.miek.nl/downloads/Go/Learning-Go-latest.pdf https://tour.golang.org http://blog.golang.org https://www.youtube.com/playlist? list=PLMW8Xq7bXrG58Qk-9QSy2HRh2WVeIrs7e https://www.youtube.com/channel/ UCx9QVEApa5BKLw9r8cnOFEA Gopher Academy: dotGo: https://gist.github.com/kachayev/21e7fe149bc5ae0bd878 Channels are not enough: http://dave.cheney.net/2015/08/08/performance- without-the-event-loop Performance without event loop:

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@antonarhipov http://www.slideshare.net/arhan https://speakerdeck.com/antonarhipov