Learn Go in 8 minutes
Manuel Duarte 💛💙
Posted on June 1, 2021
Learning the basics of Go and how it works. I chose Go as a starting language here because of its ease of use and performance.
Why Go
Go is a language that was designed at 2009 at Google by Robert Griesemer, Rob Pike, and Ken Thompson. It was created in order to address performance issues of other languages and to take advantage of the multi-core CPUs by providing concurrency out-of-the-box.
It is used to code backend components that are small, efficient with concurrency in mind. Almost all components in the Cloud-native ecosystem are written in Go (Docker, Kubernetes, Istio, Helm, Prometheus, etcd, Knative to name a few) which makes it a perfect fit for integrating with those components.
Code Style Formatting
Go language has built-in code style formatting.
VSCode has built-in integration of Go which supports formatting on-save.
Quick Language Overview
For quick language overview check this Go Programming Language Tutorial 6h video that explains all basic concepts of Go.
Below are some of those concepts:
Hello World
package main
import "fmt"
func main() {
fmt.Println("Hello World!")
}
Type go run hello.go
to execute.
Variables & Constants
package main
import "fmt"
func main() {
// A constant is a variable with a value that can't be changed
const pi float64 = 3.14159265359
// You can declare multiple variables like this
var (
varA = 2
varB = 3
)
fmt.Println(varA, varB)
// Strings are a series of characters between " or `
var Name string = "John Wick"
// Get string length
fmt.Println(len(Name))
}
Data Types
- Numeric
- int (uint8, uint16, uint32, uint64, int8, int16, int32, int64)
- float
- String
- Boolean
- true
- false
- Derived
- Pointer
- Array
- Structure
- Map
- Interface
package main
import "fmt"
func main() {
// Variable assignment with specific type
var a int = 5
var b float32 = 4.32
const pi float64 = 3.1415139475
// Variable assignment with auto type
c := 1
// Variable reassignment (should be same type as first assignment)
c = 5
// Multiple variables assignment
var (
d="hello"
e="there"
)
f,g:=14,15
fmt.Println(a)
fmt.Println(b)
fmt.Println(pi)
fmt.Println(c)
fmt.Println(d)
fmt.Println(e)
fmt.Println(f)
fmt.Println(g)
}
Operators
- Arithmetic
- addition (+)
- subtraction (-)
- multiplication (*)
- division (/)
- modulus (%)
- Relational
- greater than (>)
- lesser than (<)
- greater than or equal (>=)
- equivalence (==)
- not equals (!=)
- Logical
- and (&&)
- or (||)
- negation (!)
package main
import "fmt"
func main() {
// Arithmetic
x,y:=5,6
fmt.Println("x + y =", x + y)
fmt.Println("x - y =", x - y)
fmt.Println("x * y =", x * y)
fmt.Println("x / y =", x / y)
fmt.Println("x % y =", x % y)
isBool := true
hate := false
fmt.Println(isBool && hate)
fmt.Println(isBool || hate)
fmt.Println(!isBool)
}
Pointers
package main
import "fmt"
func main() {
x := 5
fmt.Println(x)
fmt.Println(&x)
}
Pass by value:
package main
import "fmt"
func main() {
x := 10
changeValue(x) // pass by value
fmt.Println(x) // Prints 10
}
func changeValue(x int) {
x=7
}
Pass by reference:
package main
import "fmt"
func main() {
x := 10
changeValue(&x) // pass by reference
fmt.Println(x) // prints 7
}
func changeValue(x *int) {
*x = 7
}
Printf
package main
import "fmt"
func main() {
var name string = "John Wick"
const pi float64 = 3.16412732
x := 5
isbool := true
fmt.Printf("%f \n", pi) // print float: 3.16412732
fmt.Printf("%.3f \n", pi) // print float: 3.164
fmt.Printf("%T \n", name) // print type: string
fmt.Printf("%t \n", isbool) // print boolean: true
fmt.Printf("%d \n", x) // print int: 5
fmt.Printf("%b \n", 25) // print binary: 11001
fmt.Printf("%c \n", 33) // print character: !
fmt.Printf("%x \n", 15) // print hexcode: f
}
Loops
normal for loop:
package main
import "fmt"
func main() {
for i := 1; i < 10; i++ {
fmt.Println(i)
}
}
while style loop:
package main
import "fmt"
func main() {
i := 1
for i < 10 {
fmt.Println(i)
i++
}
}
nested loops:
package main
import "fmt"
func main() {
for i := 1; i < 10; i++ {
for j := 1; j < i; j++ {
fmt.Printf("*")
}
fmt.Println()
}
}
Decision Making
package main
import "fmt"
func main() {
age := 18
if age >= 18 {
fmt.Println("you can van vote")
} else {
fmt.Println("you cannot vote")
}
}
package main
import "fmt"
func main() {
age := 18
switch age {
case 16:
fmt.Println("Prepare for college")
case 18:
fmt.Println("Don't run after girls")
case 20:
fmt.Println("Get yourself a job!")
default:
fmt.Println("Are you even alive?")
}
}
Arrays
package main
import "fmt"
func main() {
var EvenNum [5]int
EvenNum[0] = 0
EvenNum[1] = 2
EvenNum[2] = 4
EvenNum[3] = 6
EvenNum[4] = 8
fmt.Println(EvenNum[2]) // prints: 4
}
package main
import "fmt"
func main() {
EvenNum := [5]int{0, 2, 4, 6, 8}
fmt.Println(EvenNum[2]) // prints: 4
}
package main
import "fmt"
func main() {
EvenNum := [5]int{0, 2, 4, 6, 8}
for _, value := range EvenNum {
fmt.Println(value)
}
}
slices:
package main
import "fmt"
func main() {
EvenNum := [5]int{0, 2, 4, 6, 8}
for i, value := range EvenNum {
fmt.Println(value, i)
}
numSlice := []int{5, 4, 3, 2, 1}
sliced := numSlice[3:5]
fmt.Println(sliced) // prints: [2, 1]
fmt.Println(numSlice[3:]) // prints: [2, 1]
fmt.Println(numSlice[:]) // prints: [5, 4, 3, 2, 1]
fmt.Println(numSlice[0:1]) // prints: [5]
slice2 := make([]int, 5, 10)
copy(slice2, numSlice) // copies numSlice to slice2
fmt.Println(slice2) // prints [5, 4, 3, 2, 1]
slice3 := append(numSlice, 3, 0, -1)
fmt.Println(slice3) // prints [5, 4, 3, 2, 1, 3, 0, -1]
}
Maps
package main
import "fmt"
func main() {
StudentAge := make(map[string]int)
StudentAge["John"] = 23
StudentAge["Bob"] = 27
StudentAge["Anna"] = 21
StudentAge["Alice"] = 19
StudentAge["Carl"] = 42
StudentAge["Maria"] = 22
fmt.Println(StudentAge["maria"]) // not found (case-sensitive) returns: 0
fmt.Println(StudentAge["Maria"]) // found returns: 22
fmt.Println(len(StudentAge)) // returns 6 (number of elements)
}
map in a map:
package main
import "fmt"
func main() {
superhero := map[string]map[string]string{
"Superman": map[string]string{
"RealName": "Clar Kent",
"City": "Metropolis",
},
"Batman": map[string]string{
"RealName": "Bruce Wayne",
"City": "Gotham City",
},
}
if temp, hero := superhero["Superman"]; hero {
fmt.Println(temp["RealName"], temp["City"], hero)
}
}
Functions
package main
import "fmt"
func main() {
x, y := 5, 6
fmt.Println(add(x, y)) // prints: 11
}
func add(num1, num2 int) int {
return num1 + num2
}
recursion:
package main
import "fmt"
func main() {
x := 5
fmt.Println(factorial(x)) // ( factorial(5) = 5x4x3x2x1 ) prints: 120
}
func factorial(num int) int {
if num == 0 {
return 1
}
return num * factorial(num-1)
}
Defer, Recover, Panic
Control Structure:
- Defer: Defer statement defers the execution of a function until the surrounding function returns. (e.g. cleanup resources)
- Recover: Helps regain ther normal flow of execution after a panic.
- Panic: Panic is similar to throwing exception like other language.
defer:
package main
import "fmt"
func main() {
defer firstRun() // It will execute last, after secondRun() function
secondRun()
}
func firstRun() {
fmt.Println("I executed first")
}
func secondRun() {
fmt.Println("I executed second")
}
panic & recover:
package main
import "fmt"
func main() {
fmt.Println(div(3, 0))
fmt.Println(div(5, 3))
demPanic()
}
func div(num1, num2 int) int {
defer func() {
fmt.Println("div Recovered: ", recover())
}()
solution := num1 / num2 // (This will panic if num2 is 0)
return solution
}
func demPanic() {
defer func() {
fmt.Println("demPanic Recovered:", recover())
}()
panic("Paniced")
}
Structures & Interfaces
structures:
package main
import "fmt"
func main() {
rect1 := Rectangle{height: 10, width: 5}
rect2 := Rectangle{10, 5}
fmt.Println(rect1.height) // returns: 10
fmt.Println(rect1.width) // returns: 5
fmt.Println(rect2) // returns {10, 5}
fmt.Println(rect1.area()) // returns: 50
}
// Rectangle a rectangle with dimensions
type Rectangle struct {
height float64
width float64
}
func (rect *Rectangle) area() float64 {
return rect.height * rect.width
}
interfaces:
package main
import (
"fmt"
"math"
)
func main() {
rect1 := Rectangle{50, 60}
circ := Circle{7}
fmt.Println(getArea(rect1)) // returns: 3000
fmt.Println(getArea(circ)) // returns: 52.1415926535898
}
// Shape interface of a shape
type Shape interface {
area() float64
}
// Rectangle a rectangle with dimensions
type Rectangle struct {
height float64
width float64
}
// Circle a circle
type Circle struct {
radius float64
}
func (r Rectangle) area() float64 {
return r.height * r.width
}
func (c Circle) area() float64 {
return math.Pi + math.Pow(c.radius, 2)
}
func getArea(shape Shape) float64 {
return shape.area()
}
File I/O
package main
import (
"fmt"
"io/ioutil"
"log"
"os"
)
func main() {
file, err := os.Create("sample.txt")
if err != nil {
log.Fatal(err)
}
file.WriteString("Hi my name is John Wick and this file was created using GO!!")
file.Close()
stream, err := ioutil.ReadFile("sample.txt")
if err != nil {
log.Fatal(err)
}
s1 := string(stream)
fmt.Println(s1)
}
Webserver
package main
import (
"fmt"
"net/http"
)
func main() {
http.HandleFunc("/", handler)
http.HandleFunc("/hello", handler2)
http.ListenAndServe(":8080", nil)
}
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "welcome to my home page")
}
func handler2(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Hello world")
}
Posted on June 1, 2021
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