Introduction to Go - Speaker Deck

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Gabriel Sobrinho . Codeminer42 . May 2020 https://github.com/sobrinho https://twitter.com/sobrinho Introduction to Go

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Introduction • Blazing fast • Compiled • Strongly statically typed (with inference) • No exception handling • Concurrency using lightweight threads

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

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$ go run hello.go Hello, world!

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No exceptions!

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Exceptions • Use multiple return values to emulate try/catch • Use defer to emulate try/catch/ﬁnally • Defer stacks functions to be called when the closest function execution is done

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try/catch

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func main() { data, err := ioutil.ReadFile("/tmp/file") if err != nil { fmt.Println(err.Error()) return } fmt.Println(data) }

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$ go run read.go open /tmp/file: no such file or directory

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$ echo "my content" > /tmp/file $ go run read.go my content

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try/catch/finally

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func main() { defer fn(1) fmt.Println("Hello, world!") } func fn(x int) { fmt.Println(x) }

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$ go run defer.go Hello, world! 1

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func main() { defer fn(1) defer fn(2) fmt.Println("Hello, world!") defer fn(3) } func fn(x int) { fmt.Println(x) }

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$ go run defer.go Hello, world! 3 2 1

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finally the finally

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func main() { var file, err = os.OpenFile("/tmp/file", os.O_RDWR, 0644) if err != nil { fmt.Println(err.Error()) return } defer file.Close() var len, err = file.Write([]byte("my content")) if err != nil { fmt.Println(err.Error()) } }

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coroutines

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Coroutines • Lightweight threads • Used for async processing • Any function can be called in a coroutine • Communication using channels • You can wait for the result using select

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timeout

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func main() { tc := make(chan bool) rc := make(chan string) go timeout(tc) go read(rc) select { case word := <-rc: fmt.Println("Received", word) case <-rc: fmt.Println("Timeout.") } }

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func read(ch chan string) { fmt.Println("Type a word, then hit Enter.") var word string fmt.Scanf("%s", &word) ch <- word } func timeout(ch chan bool) { time.Sleep(5 * time.Second) ch <- true }

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func main() { tc := make(chan bool) rc := make(chan string) go timeout(tc) go read(rc) select { case word := <-rc: fmt.Println("Received", word) case <-tc: fmt.Println("Timeout.") } }

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$ go run concurrency.go Type a word, then hit Enter. Timeout. $ go run concurrency.go Type a word, then hit Enter. hello Received hello

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You can grossly compare Go's select{} with JavaScript's Promise.race()

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There is also sync.WaitGroup if you need to wait for a specific number of coroutines to finish Another grossly comparison to JavaScript's Promise.all()

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What have you done so far with Go? • A service that invokes a text-speech engine in macOS • A service that profile and search fingerprints using a DLL in Windows • A service that exposes local files in both platforms for reading/writing • All exposed through REST APIs in localhost

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See the pattern? You can easily expose local assets, software and hardware, to web applications!

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But that's not all...

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What the community have done so far with Go? • docker - a set of tools for deploying Linux containers • kubernetes - container management system • openshift - RedHat's PaaS • terraforma - infrastructure provisioning tool • caddy - open source HTTP/2 web server with HTTPS capability • mattermost - a teamchat system

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Who is notable using it? • Cloudﬂare • Dropbox • Google • Netﬂix • SoundCloud • Uber • And more...