Golang 101 for IT-Pros - Cisco Live Orlando 2018 - DEVNET-1808
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This session is an introduction to Golang - the Go programming language - for IT Professionals. We'll explain how to setup a GO development environment, create a simple HTTP/2 Web API, and embed our code into a Docker container. We'll also go through the reasons why the language is so popular to create network applications by showing how the language is expressive, concise, clean, and efficient. Join this session if you've started writing Python scripts that consume Web APIs, and you now want to go to the next stage by creating your own APIs to expose or store Enterprise Data. DEVNET-1808 https://www.ciscolive.com/us/learn/sessions/session-catalog/?search=DEVNET-1808
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Golang 101 for IT-Pros - Cisco Live Orlando 2018 - DEVNET-1808
- 1. #CLUS Patrick Riel, Engineer Stève Sfartz, API Evangelist DEVNET-1808 #golang for ITPros
- 2. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS /Cisco/DevNet/SteveSfartz • API Evangelist @CiscoDevNet • API Design,Architecture and Operations • WebexTeams & Devices/xAPI developer • hosted @CiscoROI: Paris Innovation Center • Node.js mainly, a bit of #golang • Europe and all over the world • github: //ObjectIsAdvantag DEVNET-1808 “vision without execution is hallucination” -- Thomas Edison mailto: stsfartz@cisco.com twitter: @SteveSfartz
- 3. Agenda © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS • Why go? • HelloWorld: install, code, compile, test • Multi-platform builds and packaging with docker • Setting up your development environment • Walkthrough: creating a command line interface • More advanced concepts: channels, go routines, … DEVNET-1808 3
- 4. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Why Go? • Released by Google in 2009 • conceived in ‘07, popular since ‘15 • Designed to address software engineering issues faced in the construction of large server software • Influenced by: C, Python, Smalltalk,Alef, CSP, Modula, Pascal… • Focus on clarity, simplicity and composability, resulting in a productive, fun, expressive and powerful language • No class inheritance. ‘Embedding’ & ‘Interfaces’ to provide polymorphism • Built-in parallelism & asynchrony via ‘Channels’ & ‘goroutines’ • Includes a - debugging, profiling, formatting and testing - toolset 4DEVNET-1808
- 5. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Software engineering guided the design of Go https://talks.golang.org/2012/splash.article • Clear dependencies • Clear syntax • Clear semantics • Composition over inheritance • Simplicity provided by the programming model (garbage collection, concurrency) • Easy tooling (the go tool, gofmt, godoc, gofix) • TRY IT: https://tour.golang.org 5DEVNET-1808
- 6. GoTour
- 7. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 7DEVNET-1808 Variables https://tour.golang.org/basics
- 8. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 8DEVNET-1808 Functions: mutiple results https://tour.golang.org/basics/6
- 9. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 9DEVNET-1808 Functions: named results https://tour.golang.org/basics/7
- 10. Setting up Go on your machine
- 11. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Installing Go https://golang.org/doc/install • Download the PKG on Mac (or MSI forWindows), and Install • by default installs in /usr/local/go (or c:Go forWindows). • adds the Go binary to your PATH environment variable • Set the GOROOT env variable if you install to a different location • Type ‘go version’ to check your installation is successful • Create a ‘go’ workspace directory • under $HOME/go on Mac (or %USERPROFILE%go forWindows) • Set a GOPATH environment variable is preferable (and mandatory if elsewhere) • Add the $GOPATH/bin directory to your path 11DEVNET-1808
- 12. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS HelloWorld (on a Mac) • Create a “src/hello” directory in your workspace • Create a file named hello.go • Build it with the go tool • Produces an executable named hello • Run go install to install the binary into your workspace's bin directory or go clean to remove it. 12DEVNET-1808 1 File: src/hello/hello.go 2 3
- 13. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS HelloWorld (on Windows) • Create a “src/hello” directory in your workspace • Create a file named hello.go • Build it with the go tool • Produces an executable named hello.exe • Run go install to install the binary into your workspace's bin directory or go clean to remove it. 13DEVNET-1808 1 2 File: src/hello/hello.go 3
- 14. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Typical go folder structure https://golang.org/doc/code.html • go tooling requires to organize your code in a specific way • Go programmers typically keep all their Go code in a single workspace. • A workspace contains many version control repositories (managed by git, for example). • Each repository contains one or more packages. • Each package consists of one or more Go source files in a single directory. • The path to a package's directory determines its import path. 14DEVNET-1808 GOPATH = C:Localgowork mkdir ‘$GOPATH/src/github.com/<username>/hello’
- 15. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Creating a Library https://golang.org/doc/code.html > mkdir $GOPATH/src/github.com/<user>/hello 15DEVNET-1808 filename: hello.go
- 16. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Creating a Library https://golang.org/doc/code.html > mkdir $GOPATH/src/github.com/<user>/stringutil 16DEVNET-1808 filename: reverse.go
- 17. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Creating a Library https://golang.org/doc/code.html > go install github.com/<user>/hello • the ‘stringutil’ package is automatically installed as well • go executables are statically linked 17DEVNET-1808
- 18. Setting up your development environment
- 19. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Go Extension forVisual Studio Code 19DEVNET-1808 Installs automatically at launch or manually via go get –v: github.com/nsf/gocode github.com/uudashr/gopkgs/cmd/gopkgs github.com/ramya-rao-a/go-outline github.com/acroca/go-symbols golang.org/x/tools/cmd/guru golang.org/x/tools/cmd/gorename github.com/fatih/gomodifytags github.com/haya14busa/goplay/cmd/goplay github.com/josharian/impl github.com/rogpeppe/godef golang.org/x/tools/cmd/godoc sourcegraph.com/sqs/goreturns github.com/golang/lint/golint github.com/cweill/gotests github.com/derekparker/delve/cmd/dlv golang.org/x/tools/cmd/guru
- 20. Demo
- 21. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS VS Code golang extension: InstallationTips • If any go tools dependency is missing, install it manually • Make sure the $GOPATH/bin directory appears in your path • To install the Delve debugger, type > go get -u github.com/derekparker/delve/cmd/dlv • If having issue with the debugger on Mac: ‘lldb-server’ not found, type > xcode-select –install 21DEVNET-1808
- 23. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Packaging for various platforms • The go toolchain natively cross-build executables for any Go-supported foreign platform • Example: > env GOOS=linuxGOARCH=amd64 go build -o dist/demo.linux -v main.go https://www.digitalocean.com/community/tutorials/how-to-build-go-executables- for-multiple-platforms-on-ubuntu-16-04 DEVNET-1808
- 24. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS DEVNET-1808 Dockerfile example https://github.com/ObjectIsAdvantag/CLEUR-1814/tree/master/8-docker
- 25. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 25DEVNET-1808 Pointers https://tour.golang.org/moretypes/1
- 26. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 26DEVNET-1808 readword.go
- 27. CLI with golang doing chatops
- 28. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Methods and Interfaces • Remember: a method is just a function with a receiver argument • To implement an interface inGo • Implement all the methods in the interface 28DEVNET-1808 https://tour.golang.org/methods https://gobyexample.com/interfaces https://github.com/ObjectIsAdvantag/CLEUR-1814/blob/master/7-spark/main.go https://github.com/ObjectIsAdvantag/CLEUR-1814/blob/master/6-interfaces/main.go
- 29. CLI Demo
- 30. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 30DEVNET-1808 Defer https://tour.golang.org/flowcontrol/12
- 31. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Defer • defers the execution of a function until the surrounding function returns • deferred function calls are pushed onto a stack (executed in LIFO) 31DEVNET-1808 counting done 5 4 3 2 1 0
- 32. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS HTTP API Clients • simplify development • speed up development • clean code • abstraction https://www.scaledrone.com/blog/posts/creating-an-api-client-in-go 32DEVNET-1808
- 33. Advanced #golang
- 34. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 34DEVNET-1808 Concurrency: channels & go routines
- 35. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 35DEVNET-1808 Structures https://tour.golang.org/moretypes/2
- 36. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 36DEVNET-1808 Arrays https://tour.golang.org/moretypes/6
- 37. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 37DEVNET-1808 Slices https://tour.golang.org/moretypes/13
- 38. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 38DEVNET-1808 Maps https://tour.golang.org/moretypes/22
- 39. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS 39DEVNET-1808 Closures https://tour.golang.org/moretypes/25
- 40. Wrapup
- 41. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Wrapup… go for ITPros CLI Proxy Reverse Proxy Web API 41DEVNET-1808
- 42. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS State of go – 2017 user survey • Continued growth in the language • Enterprise-ready: for the first time, more Go at work than home • Top-uses of Go is now writingAPI/RPC services • 2016 was stillCLI. Now taking advantage of the distinguishing features of Go, key elements of cloud computing • Biggest challenges: lack of dependency management, generics • 64% responses use Go on Linux, 49% on MacOS, 18% onWindows • VSCode is now the most popular editor for Go developers • Finding answers:Go website, Stack Overflow, and reading code • Primary news sources: Go blog, Reddit, andTwitter 42DEVNET-1808
- 43. © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Cisco Community Contributions • golang samples • https://github.com/ObjectIsAdvantag/CLEUR-1814 • Cisco Spark REST API wrapper • https://github.com/jbogarin/go-cisco-spark • CiscoACI from golang • https://github.com/udhos/acigo • Answering Machine backed byTropo • https://github.com/ObjectIsAdvantag/answering-machine • Proxy incoming web hooks to established web sockets • https://github.com/sgrimee/whproxy 43DEVNET-1808
- 44. Complete your online session evaluation © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public#CLUS Give us your feedback to be entered into a Daily Survey Drawing. Complete your session surveys through the Cisco Live mobile app or on www.CiscoLive.com/us. Don’t forget: Cisco Live sessions will be available for viewing on demand after the event at www.CiscoLive.com/Online. DEVNET-1808
- 45. Q&A
- 46. Thank you #CLUS
- 47. #CLUS
Editor's Notes
- Examples with what’s in the standard golang box Logs: https://github.com/sirupsen/logrus
- https://talks.golang.org/2012/splash.article
- Rather do ‘ $GOPATH/src/github.com/<username>/hello’
- Rather do ‘ $GOPATH/src/github.com/<username>/hello’
- https://cloud.google.com/appengine/docs/standard/go/tools/uploadinganapp
- Pass by value is not ineficient in many cases, or mandates to create placeholders / shared variables, or even understand the context of the stack in JS
- package main import ( "fmt" ) func readword() (word string) { fmt.Println("Type something") fmt.Scanf("%s", &word) return } func main() { w := readword() fmt.Println("You entered", w) }
- Makes your code more elegant
- package main import ( "fmt" "time" ) func timeout(t chan bool) { time.Sleep(5 * time.Second) t <- true } func readword(ch chan string) { fmt.Println("Type something and hit Enter") var word string fmt.Scanf("%s", &word) ch <- word } func main() { t := make(chan bool) go timeout(t) ch := make(chan string) go readword(ch) select { case word := <-ch: fmt.Println("Received", word) case <-t: fmt.Println("Timeout.") } }
- For JS familiar developers