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#golang
Pascal C/Asm Perl Java
Evolution of a software developer
PaintGo
A little bit of history…
2007 2009 2012 2013 2015
The beginning
Open sourced
1.0 1.1 1.5
Where used?
https://github.com/golang/go/wiki/GoUsers
Google, Docker, Heroku, Cloud Foundry, CoreOS, InfluxDB, Dropbox, OpenShift, SoundCloud, Toggl, etc.
In the clouds!
“Can't reach the pedals. no brakes. gaining speed. eyes bulging in horror. technical debt crash eminent. “
— Tim Dysinger, @dysinger
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.”
“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
package main
import "fmt"
func main() { fmt.Println("Hello, Devclub!") }
package main
import "fmt"
func main() { fmt.Println("Hello, Devclub!") }
Java-developers reaction to the capital letter in a function name
Missing stuffNo classes
No generics
No inheritance
No method overriding
No exceptions
etc
No generics? No exceptions? Wut!?
FeaturesFunctions
Structures
Interfaces
Methods
Slices
Pointers
Go-routines
Channels
func main() { fmt.Println("1 + 2 =", add(1, 2)) }
func add(a int, b int) int { return a + b }
Functions
func main() { fmt.Println("1 + 2 =", add(1, 2)) }
func add(a int, b int) int { return a + b }
Functions
func main() { fmt.Println("1 + 2 =", add(1, 2)) }
func add(a, b int) int { return a + b }
Functions
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
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
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
func main() { double := func(a int) int { return a * 2 } double(14) }
Functions as values
func main() { double := factory() double(14) }
func factory() func(a int) int { return func(a int) int { return a * 2 } }
Functions as values
Arraysvar 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"}
Slicesa := []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]
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) }
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) } Obligatory comma!?
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
Pointers
var p *int
i := 42 p = &i fmt.Println(*p) *p = 21 fmt.Println(i)
42
21
Pointers
var p *int
i := 42 p = &i fmt.Println(*p) *p = 21 fmt.Println(i)
Pointers
var p *int
i := 42 p = &i fmt.Println(*p) *p = 21 fmt.Println(i)
No pointer arithmetics
Structurestype Vertex struct { X int Y int }
Structurestype Vertex struct { X int Y int }
func main() { fmt.Println(Vertex{1, 2}) }
Methodstype Vertex struct { X int Y int }
func (v Vertex) Total() int { return v.X + v.Y }
Methodstype Vertex struct { X int Y int }
func (v Vertex) Total() int { return v.X + v.Y }
v := Vertex{1, 2} v.Total()
Interfaces
type Entity interface { Total() int }
Interfaces
type Entity interface { Total() int }
Vertex implements Entity
func (v Vertex) Total() int { return v.X + v.Y }
Interfaces
v := Vertex {1, 2} blah(v)
func blah(e Entity) { e.Total() }
Interfaces
func foo(x interface{}) int { x.(Vertex).Total() }
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})
A programmer had a problem. He thought to solve it with threads.
two Now problems. he has
Go-routines
foo(Vertex2{1,2})
go foo(Vertex2{1,2})
Usual function call
Function call in a go-routine
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
Channelsci := 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
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 }
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 }
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 }
Start go-‐routines
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 }
Send values
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 }
Receive values and print
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 }
Done!
Environment
Environment
Tooling
• go (version, build, test, get, install, …)
• gofmt
• godoc
• Editors (vim, atom, IntelliJ IDEA, Sublime Text)
My choice
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
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
Testingpackage 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") } }
Testingpackage 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
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 :)
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
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?
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
Resourceshttp://www.miek.nl/downloads/Go/Learning-Go-latest.pdfhttps://tour.golang.org
http://blog.golang.orghttps://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:
@antonarhipovhttp://www.slideshare.net/arhan https://speakerdeck.com/antonarhipov
