Workshop: Introduction to
the Programming Language
Go

Marcel Schneider

Agenda for today

1. Intro
2. Go Basics & Soundex
3. Coffee Break
4. Object Orientation & Movie Database
5. Concurrency & Website Checker
6. Cool Down & Feedback

Goals of this Workshop

• Learn the Basics of Go
• Write, compile and run Go Apps
• Create a REST Webservice with Go
• Understand Error Handling, Testing, Object Orientation and Concurrency in Go

Tools you need locally

• Latest Go Version
• IDE (maybe VS Code or Goland/IntelliJ)
• Git

Helpful Links

Go History

Companies using Go

Motivation behind Go

• Dissatisfaction with existing Programming Languages like C++/Java
• address Pain Points in large scale Software Development
• "Language Design in the Service of Software Engineering" (Rob Pike)

Go Features

• Compilation into Machine Code
• static Typing (with Type Inference)
• Concurrency with lightweight Threads
• automatic Garbage Collection
• built-in Dependency Management
• completely OpenSource (BSD License)
• extensive standard Library (pkg.go.dev)

DEMO: Hello World

Language Characteristics

• Data Types: Basic Types, Arrays, Maps and Structs
• Pointers, but no Pointer Arithmetics
• C-inspired Syntax
• Packages used for Structuring Source Files
• Generics (since Release 1.18 on 15.03.2022)
• General: Focus on Minimalism and Simplicity

Exercise 1a: Soundex

• Phonetic Algorithm for Indexing Names by Sound, as pronounced in English
• Description of (engl.) Soundex Algorithm, see https://de.wikipedia.org/wiki/Soundex
• Examples: Golang → G452, Soundex → S532

Exercise 1a: Soundex Algorithm

• first Letter uppercase, followed by exactly 3 Numbers (Soundex → S532)
• Mapping of Letters see Table
• no Mapping for A/E/I/O/U/H/W/Y
• no consecutive equal Numbers
• ensure length 4, add Zeros or cut
• Hallo → H400, Entwicklertag → E532

Exercise 1a: Soundex Setup

1. git clone -b workshop
   github.com/bridgingit-gmbh/go-workshop
2. cd go-workshop/soundex-go
3. go build
4. ./soundex-go (.exe on Windows)

user@pc % ./soundex-go
implement me
            

Exercise 1a: Soundex Coding

• Implement the Function in soundex.go

  
  package soundex
  
  func Soundex(input string) string {
      return "implement me"
  }
                      

• Test your implementation
  

  
  user@pc % go test
  ok github.com/go-workshop/soundex-go/soundex 0.303s
                      

Error Handling

• no try/catch, no Exceptions
• Error as additional Return Type
• Error == nil means no Error

type error interface {
    Error() string
}
            

DEMO: Error Handling

Exercise 1b: Soundex Errors

• adjust Signature of Soundex Function

  
  package soundex
  
  func Soundex(input string) (string, error) {
      //your code here
      return result, err
  }
                    

• return Error on empty Input String
• check return values in main() and print the error
• add a test for the error case

Exercise 1c: Soundex Testify

• add Dependency: go get github.com/stretchr/testify → see updated go.mod
• use testify Assertions in your Tests
• update all dependencies: go get -u
• cleanup dependencies: go mod tidy

Next Topic: Object Orientation

• supported, but without Classes
• Methods can be defined on Structs
• Composition over Inheritance
• implicit Interface Implementation

DEMO: Object Orientation

Exercise 2: Movie Database

• REST Webservice which manages Movie Data
• HTTP Request Mapping with Go Standard Library
• Usage of hardcoded Example Movies

Exercise 2: Implement REST Call

1. navigate to Subfolder moviedb-go
2. implement Endpoint GET /movies/{id}
3. create InMemoryRepository (File inmemory.go) which fulfills the existing Interface MovieRepository
4. see example-data.go for movie test data
5. test the Implementation with your Browser

Next Topic: Concurrency

• Goroutine: lightweight Thread managed by the Go Runtime
• sync Package with Mutex/Locks and WaitGroups
• Concept of Channels for Goroutine Communication
• "Don't communicate by sharing Memory, share Memory by Communicating" (Rob Pike)

Demo: Channel

Exercise 3: Website Checker

• App which checks the Reachability of Websites
• currently the App executes the Checks sequentially
• Goal: Execute the Checks concurrently and use Channel Synchronization

Exercise 3: Website Checker

1. navigate to Subfolder website-checker-go
2. run the Checks concurrently
3. transmit the Results to a Channel
4. receive Results in main() and print them
5. compare Running Time sequential vs. concurrent

Conclusion and Feedback

• Small Memory Footprint and fast Startup Time
• Lightweight Ecosystem
• Good online Documentation
• What did You like in Go (or not)?