Go Basics Workshop

Transcript

1. Go Basics Workshop #NarF
2. Golang 2
3. Golang • compiled language • fast compilation • based on C & Oberon • v1 release 2012 3
4. Golang • garbage collection • type safety • has pointers ! • concurrency with goroutines • object oriented but not class based 4
5. Get GOing 5
6. The basics - package declaration package main import "fmt" func main() { fmt.Printf("Hello World!") } 6
7. The basics - imports package main import "fmt" func main() { fmt.Printf("Hello World!") } 7
8. The basics - main function package main import "fmt" func main() { fmt.Printf("Hello World!") } 8
9. Variables var abc string = "a string variable" var number int // number = 0 var emptyString string // emptyString = "" short := "a string variable" // var short string = "a string variable" 9
10. Variables var abc string = "a string variable" var number int // number = 0 var emptyString string // emptyString = "" short := "a string variable" // var short string = "a string variable" 10
11. Variables var abc string = "a string variable" var number int // number = 0 var emptyString string // emptyString = "" short := "a string variable" // var short string = "a string variable" 11
12. Arrays // have a fixed size types := [5]int // [0 0 0 0 0] // values can be changed and retrieve types[2] = 3 // [0 0 3 0 0] val := types[2] // 3 // can be initialized on delaration types := [5]int{1, 2, 3, 4, 5} // [1 2 3 4 5] // can have more dimensions more := [2][3]int 12
13. Arrays // have a fixed size types := [5]int // [0 0 0 0 0] // values can be changed and retrieve types[2] = 3 // [0 0 3 0 0] val := types[2] // 3 // can be initialized on delaration types := [5]int{1, 2, 3, 4, 5} // [1 2 3 4 5] // can have more dimensions more := [2][3]int 13
14. Arrays // have a fixed size types := [5]int // [0 0 0 0 0] // values can be changed and retrieved types[2] = 3 // [0 0 3 0 0] val := types[2] // 3 // can be initialized on delaration types := [5]int{1, 2, 3, 4, 5} // [1 2 3 4 5] // can have more dimensions more := [2][3]int 14
15. Arrays // have a fixed size types := [5]int // [0 0 0 0 0] // values can be changed and retrieve types[2] = 3 // [0 0 3 0 0] val := types[2] // 3 // can be initialized on delaration types := [5]int{1, 2, 3, 4, 5} // [1 2 3 4 5] // can have more dimensions more := [2][3]int 15
16. Slices slice1 := make([]string, 3) // ["" "" ""] slice2 := []string{"a", "b", "c"} // ["a" "b" "c"] slice1[0] = "a" // ["a" "" ""] var length = len(slice1) // 3 slice2 = append(slice2, "d") // ["a" "b" "c" "d"] 16
17. Slices slice1 := make([]string, 3) // ["" "" ""] slice2 := []string{"a", "b", "c"} // ["a" "b" "c"] slice1[0] = "a" // ["a" "" ""] var length = len(slice1) // 3 slice2 = append(slice2, "d") // ["a" "b" "c" "d"] 17
18. Slices slice1 := make([]string, 3) // ["" "" ""] slice2 := []string{"a", "b", "c"} // ["a" "b" "c"] slice1[0] = "a" // ["a" "" ""] var length = len(slice1) // 3 slice2 = append(slice2, "d") // ["a" "b" "c" "d"] 18
19. Slices slice1 := make([]string, 3) // ["" "" ""] slice2 := []string{"a", "b", "c"} // ["a" "b" "c"] slice1[0] = "a" // ["a" "" ""] var length = len(slice1) // 3 slice2 = append(slice2, "d") // ["a" "b" "c" "d"] 19
20. Slices - slice slice := []string{"a", "b", "c", "d", "e", "f"} // [a b c d e f] slice[2:5] // [c d e] slice[2:] // [c d e f] slice[:5] // [a b c d e] 20
21. Slices - slice slice := []string{"a", "b", "c", "d", "e", "f"} // [a b c d e f] slice[2:5] // [c d e] slice[2:] // [c d e f] slice[:5] // [a b c d e] 21
22. Slices - slice slice := []string{"a", "b", "c", "d", "e", "f"} // [a b c d e f] slice[2:5] // [c d e] slice[2:] // [c d e f] slice[:5] // [a b c d e] 22
23. Slices - slice slice := []string{"a", "b", "c", "d", "e", "f"} // [a b c d e f] slice[2:5] // [c d e] slice[2:] // [c d e f] slice[:5] // [a b c d e] 23
24. Maps m := make(map[string]int) m["foo"] = 1 // map[foo:1] m["bar"] = 2 // map[foo:1 bar:2] len(m) // 2 delete(m, "foo") // map[bar:2] val, ok := m["bar"] // 2, true 24
25. Maps m := make(map[string]int) m["foo"] = 1 // map[foo:1] m["bar"] = 2 // map[foo:1 bar:2] len(m) // 2 delete(m, "foo") // map[bar:2] val, ok := m["bar"] // 2, true 25
26. Maps m := make(map[string]int) m["foo"] = 1 // map[foo:1] m["bar"] = 2 // map[foo:1 bar:2] len(m) // 2 delete(m, "foo") // map[bar:2] val, ok := m["bar"] // 2, true 26
27. Maps m := make(map[string]int) m["foo"] = 1 // map[foo:1] m["bar"] = 2 // map[foo:1 bar:2] len(m) // 2 delete(m, "foo") // map[bar:2] val, ok := m["bar"] // 2, true 27
28. Maps m := make(map[string]int) m["foo"] = 1 // map[foo:1] m["bar"] = 2 // map[foo:1 bar:2] len(m) // 2 delete(m, "foo") // map[bar:2] val, ok := m["bar"] // 2, true 28
29. Loops - classic while i := 0 for i <= 3 { i = i + 1 } 29
30. Loops - classic for for i := 0; i <= 3; i++ { fmt.Println(i) } 30
31. Loops - range numbers := []int{1, 2, 3} sum := 0 for i, val := range numbers { fmt.Println("index:", i) sum += val } fmt.Println("sum:", sum) 31
32. Functions func sum(a int, b int) int { return a + b } // or func sum(a, b int) int { return a + b } 32
33. Multiple return values func fancySum(a int, b int) (int, bool) { ok := true // some error checks return a + b, ok } func main() { sum, ok := fancySum(1, 2) if !ok { // fail with error } } 33
34. Structs type person struct { firstname string lastname string age int } person1 := person{firstname: "John", lastname: "Doe", age: 28} person2 := person{"Jane", "Doe", 28} fmt.Println(person1.age) 34
35. Structs composition type Model struct { ID int CreateDate time.Time ChangeDate time.Time } 35
36. Structs composition type Model struct { ID int CreateDate time.Time ChangeDate time.Time } type User struct { Model Firstname string Lastname string } 36
37. Structs composition user := User{ ID: 1, Firstname: "John", Lastname: "Doe", CreateDate: time.Now(), ChangeDate: time.Now(), } user.ID == user.Model.ID // true 37
38. Interfaces type animal interface { color() string } 38
39. Interfaces type cat struct { name string } type mouse struct { name string } 39
40. Interfaces func (c cat) color() string { if c.name == "Kitty" { return "black" } return "white" } func (m mouse) color() string { return "grey" } 40
41. Interfaces func print(a animal) { fmt.Println(a.color()) } func main() { c1 := cat{"Kitty"} c2 := cat{"Miau"} m := mouse{"Pinky"} print(c1) // black print(c2) // white print(m) // grey } 41
42. Hands On #1 calc 15 min 42
43. Hands On #1 • Add • Sub • Mul • Div • Fib - iterativ 43
44. Building an API • DB Access • HTTP + Routing • jsonapi encoding 44
45. Hands On #2 Company API 30 min 45
46. Company API • gorm.io • github.com/gorilla/mux • github.com/google/jsonapi { "data": { "id": 1, "type": "company", "attributes": { "name": "karriere.at", "zip": "4020", "city": "Linz" } } } 46
47. Goroutines • concurrent execution of code • synchronization needed for shared resources (mutex, lock) 47
48. Goroutines func doSomeWork() { for i := 0; i < 5; i++ { fmt.Println("Work index:", i) } } func main() { go doSomeWork() // continue with main thread flow } 48
49. Channels • used for communication between goroutines • sender sends messages, receiver reads from channel • channels are basically blocking except they are buffered 49
50. Channels // create a channel messages := make(chan string) // send a message messages <- "a message" // read a message msg := <- messages 50
51. Channels // create a channel messages := make(chan string) // send a message messages <- "a message" // read a message msg := <- messages 51
52. Channels // create a channel messages := make(chan string) // send a message messages <- "a message" // read a message msg := <- messages 52
53. Demo Time Goroutines 53
54. Tooling for Go • code formating • linting • testing • benchmarking • documentation • profiling 54
55. my golang favorites • strong type system • error handling/multiple return values • implicit interfaces • built-in tooling • concurrency • speed 55
56. Helpful resources • A Tour of Go https://tour.golang.org • Go by Example https://gobyexample.com • List of Go Books https://github.com/dariubs/GoBooks 56
57. Thanks for listening @fetzi_io 57