coding-leipzig.slide

Go in 30 min

by Michael Panzer
https://twitter.com/panzer_michael
https://www.meetup.com/de-DE/Leipzig-Golang-and-Cloud/

* About me
- started with Java/Android
- Go for about 4 years for fun and about 2 for prod

* What's up today?
- Basic language constructs
- Examples...

* Go Tool (current 1.11)
- mod - dependency management with modules (since 1.11)
- fmt - apply default Code Style
    $ go fmt main.go
- run - run main.go file
    $ go run main.go
- build - builds executable
    $ go build
    # Crosscompiling
    $ env GOOS=windows GOARCH=amd64 go build # win 64bit
    $ env GOOS=linux GOARCH=arm GOARM=5 go build # raspi 32bit

* Hello World
.play hello/hello-world.go


* Hello World
.play hello/hello-world.go

Packages

    package main

- Code organized in packages
- One Package 1 to n go files are in the same package
- Last folder name must be equal to package name

* Hello World
.play hello/hello-world.go

Call things from package

    fmt.Println("Hello World!")

- Case on first letter defines package private/public
    fmt.Println("Hello World!") <- callable outside the package

    fmt.println("Hello World!") <- callable ONLY inside the package


* Hello World
.play hello/hello-world.go

Import

    import "fmt"
    - or multiple -
    import (
        "fmt"
        "os"
    )

* Hello World
.play hello/hello-world.go

    func main() {}

- Main func entrypoint to program
- Program ends when main returns
- Everything running outside will be just killed

* Build-in types

    bool

    string

    int  int8  int16  int32  int64
    uint uint8 uint16 uint32 uint64 uintptr

    byte // alias for uint8

    rune // alias for int32
         // represents a Unicode code point

    float32 float64

    complex64 complex128

* Variables
.play types/var.go
- Not compiling with unused variable

* Functions

    func (N|n)ame(name type) (type)

- multiple input and multiple returns
- first name then type of the parameter

.code types/func_1.go

* Functions

Functions can be used like any other variable
.code types/func_4.go

* Functions

func can be passed as parameter to another func

.code types/func_2.go
.code types/func_3.go

* Structs
.code types/structs_1.go

- can have multiple fileds of any type
- NO inheritance
- NO constructor

.code types/structs_2.go
- trailing comma

* Structs
.play types/structs_0.go /START OMIT/,/END OMIT/

* Structs
.play types/structs_3.go /START OMIT/,/END OMIT/

* Structs
.play types/structs_4.go /START OMIT/,/END OMIT/

* Pointer
.play types/pointer.go

* Slices
.play types/slice_1.go

* For
.code control/iter_0.go

* For range
.play control/range.go

* If
.play control/if.go

* Switch
.play control/switch_1.go

* Maps
.play types/maps_1.go

* Interface
.play -edit interfaces/animal.go /START OMIT/,/END OMIT/

* Errors
.play -edit types/errors.go
- Errors are values
- Always handle errors
- Usually the last return value if there can be an error
- Early exit not - Happy path if-Spaghetti <<---- WHAT?

* Go Go Go

- Goroutine are used for concurrency
- Any func can be executed executed concurrently
- Keyword is -> go
    go func()
- very low overhead so a lot of Goroutines are possible
- async IO (looks blocking is non blocking)

* Let's Go
.play -edit concurrency/go_1.go

* Let's Go.. Wait..
.play -edit concurrency/go_2.go

* WaitGroup
.play -edit concurrency/go_4.go /START OMIT/,/END OMIT/

* Channels
    don't communicate by sharing memory share memory by communicating
- Channel is typed with a bool for example
    c := make(chan bool)
- Channel is like a Stack (with optional size)
- Pop on one side, Push on other side
    c <- true (push - write)
    v := <- c (pop - read)
- Pop/Push bloking when size 0
    c <- true (will block forever)

* Channels
.play -edit concurrency/go_5.go /START OMIT/,/END OMIT/

* Select Channels
.play -edit concurrency/go_6.go /START OMIT/,/END OMIT/

* Collector
.play -edit concurrency/go_8.go /START OMIT/,/END OMIT/

* Simple Server
.play -edit webserver/server.go /START OMIT/,/END OMIT/

* Thrilled?

Leipzig Golang and Cloud Native Meetup #2
Freitag, 15. März 2019

.image cloud-native-and-golang-leipzig-preview.png