Golang Cheat Sheet 🏷️

bool, string,
int, int8, int16, int32, int64,
uint, uint8, uint16, uint32, uint64, uintptr,
rune, byte,
float32, float64,
complex64, complex128

var user = "ABC"
var class, age = 5, 10
var isAdult bool
hobby := "painting"
fmt.Println(user, class, age, isAdult, hobby)
// ABC 5 10 false painting

const APP string = "Golang app"
const port = 9001
fmt.Printf("%T\n", port)

isAdult := true
for isAdult {
  fmt.Println("Ready to vote!")
  isAdult = false
}
for class := 1; class < 10; class++ {
  fmt.Println(class)
  fmt.Println("class")
}
for {
  fmt.Println("I’m infinite loop, with a break")
  break
}

// to create an empty map, use the built-in make
class := make(map[string]int)
class["Johnny"] = 7
class["Jeo"] = 10
fmt.Println(class)
fmt.Println(len(class))
fmt.Println(len(class))
delete(class, "Johnny") // deleting key
fmt.Println(len(class))

// present value in the map
_, ok := class["Jeo"]
fmt.Println(ok)
// another way of initializing maps
moreClass := map[string]int{"Bob": 8, "Any": 3}
fmt.Println(moreClass)

type user struct {
  name string
}

bob := user{"Bob"}
bobPointer := &bob
tommyPointer := &user{"Tommy"}
var userPointer *user = new(user)

func eating(user string, food string) string {
  return fmt.Sprintf(user + "is eating" + food)
}

// multiple return values
func isAdult(age int) (int, bool) {
  if age > 18 {
    return age, true
  }
  return age, false
}

// variadic functions
func good(students ...string) {
  for _, student := range students {
    fmt.Println("This is good student", student)
  }
}
func main() {
  work := eating("Bob", "Jon")
  age, valid := isAdult(11)
  fmt.Println(work, age, valid)
  good("Bob", "John")
  good("Bob", "John", "Any", "Tom")

  // if you already have multiple args in a slice, using func(slice...)
  students := []string{"Bob", "John", "Any"}
  good(students...)
  // closures
  goodChecker := good
  goodChecker(students...)
  func() {
    fmt.Println("Printing good students...")
  }()
}

name := "Jon"
switch name {
case "Jon":
  fmt.Println("Good student")
case "Bob":
  fmt.Println("Average student")
}

age := 9
switch {
case age > 17:
  fmt.Println("Adult")
default:
  fmt.Println("Minor")
}

// an array of elements of a specific length
var students [3]string
fmt.Println(len(students))
students[0] = "John"
fmt.Println(students)
fmt.Println(students[0])
fmt.Println(len(students))
moreStudents := [3]string{"Any", "Tom", "Bob"}
fmt.Println(moreStudents)

// 2D array
var scoreMatrix [2][3]int
for i := 0; i < 2; i++ {
  for j := 0; j < 3; j++ {
    scoreMatrix[i][j] = i + j
  }
}

// a slice doesn’t need a specific length
var students []string
fmt.Println(len(students))
students = append(students, "Bob")
fmt.Println(len(students))

type user struct {
  name  string
  age int
}

func main() {
  fmt.Println(user{name: "Bob", age: 25})
  fmt.Println(user{name: "Any", age: 31})

  // omitted fields will be zero-valued initialized
  fmt.Println(user{name: "John"})
  tom := user{name: "Tom", age: 50}
  fmt.Println(tom.age)
  tom.age = 51
}

type user interface {
  isGood()
}
type goodStudent struct{}

func (g goodStudent) isGood() {
  fmt.Println("Good student")
}

type averageStudent struct{}

func (a averageStudent) isGood() {
  fmt.Println("Average Student")
}
func main() {
  students := []user{
    goodStudent{},
    averageStudent{},
  }
  for _, student := range students {
    student.isGood()
  }
}

func isGood(name string) {
  fmt.Println("This is good student", name)
}
func main() {
  go isGood("Bob")
  time.Sleep(time.Second)
}

func isAdult(name string, valid chan bool) {
  time.Sleep(time.Second)
  fmt.Println("This student is adult", name)
  valid <- true
}
func main() {
  // un-buffered channels
  validSignal := make(chan bool)
  name := "Bob"
  go isAdult(name, validSignal)
  fmt.Println(<-validSignal)

  // buffered channels
  oneSignal := make(chan bool, 1)
  oneSignal <- true
  fmt.Println(<-oneSignal)

  // closing channel to prevent deadlocks
  oneSignal <- true
  close(oneSignal)

  for message := range oneSignal {
    fmt.Println(message)
  }
}