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What is Go?
- Simple but fast, popular programming language for cloud engineering
- statically typed, compiled programming language
- Developed by google in 2007
- Open sourced in 2009
- Often known as golang
- Syntax has similarity with C,C++
- Mainly used as a server side or backend language
- Supports cross-os
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Why Go?
- For making simple, reliable and efficient computer program/software
- Helps to create high performance applications but use less resources
- It helps to write concurrent multithread programs
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Prerequisities
- Nothing, but knowing C/C++ or any programming language is an advantage
- package declaration - every go program is consist of packages. it is a mandatory thing. it has to be the first statement of go program.
- import packages
- function
- statement
// main.go
package main
import “fmt”
func main() {
fmt.Println(“My name is Anisul Islam”)
}
output: My name is Anisul Islam- IDE / Text Editor -> Any text editor- notepad / notepad++ / VSCode (free), Vim (free) / GoLand (paid)
- Go compiler -> compiler translate the source code into machine/executable code so that machine can understand the instructions
- go extension for VSCode
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A simple go program
// filename: main.go // a program for printing student details package main import "fmt" func main() { fmt.Println("Anisul Islam is a student") fmt.Println("Anisul Islam is 32 years old") fmt.Println("Anisul Islam has got GPA 3.92/5 in SSC") fmt.Print("Anisul Islam originally from Bangladesh"); }
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running the program
- go mod init project-name
- go run fileName.go
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Token of any programming language
- keywords
- data types
- variables
- Escapse sequences
- operators
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escape sequences example
package main import "fmt" func main(){ fmt.Print("Name \t Age\n") fmt.Print("----- \t ------\n") fmt.Print("Anis \t 32\n") fmt.Print("Rakib \t 29\n") }
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there are 2 types of comment is available in Go -> single line, multiple line comment. comments are ignored by the compiler.
// single line comment /* multiple line comment */
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keywords: keywords are reserved words.
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Data types: boolean, string, numeric - integer, floating, derived types - pointer, array, structure, slice, map, interface etc.
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example of data types
"anisul islam" -> string type 21 -> int type 21.5 -> floating type true/false -> bool // more on int, float variation of integer-> int8 (8 bits), int16, int32, int64, uint8 (only positive 0 to 255), uint6, uint32, uint64 variation of float-> float32, float64
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syntax of variable declaration: var variable1, variable2, ... variableN dataType
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variable naming convention (camelcasing)
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example
package main import "fmt" func main(){ // static variable declaration var name, country string var age int var gpa float32 // variable initialization name = "anisul islam" country = "Bangladesh" age = 32 gpa = 3.92 // dynamic variable declaration + initialization // var name = "Anisul Islam" // var country = "Bangladesh" // var age = 32 // var gpa = 3.92 // var name,country,age,gpa = "anisul islam", "Bangladesh", 32, 3.92 // shortcuts // name := "Anisul Islam" // country := "Bangladesh" // age := 32 // gpa := 3.92 fmt.Println(name) fmt.Println(name, " is a student") fmt.Println(name,"is", age, "years old") fmt.Println(name, "has got" , gpa, "/5 in SSC") fmt.Print(name,"originally from ", country); }
package main
import "fmt"
func main(){
name := "Anisul Islam"
country := "Bangladesh"
age := 32
gpa := 3.92
fmt.Printf("%v is a student\n", name)
fmt.Printf("%v is %v years old\n", name, age)
fmt.Printf("%v has got GPA %v/5 in SSC\n", name, gpa)
fmt.Printf("%v originally from %v\n", name, country);
}-
Constants indicate to fix values
package main import "fmt" func main(){ var name string const COUNTRY = "Bangladesh" var age, num1, num2 int var gpa float32 fmt.Printf("Enter your name: ") fmt.Scanf("%v", &name) fmt.Printf("Enter your age: ") fmt.Scan(&age) fmt.Printf("Enter your SSC gpa: ") fmt.Scanln(&gpa) fmt.Printf("Enter 2 numbers: ") fmt.Scan(&num1, &num2) fmt.Printf("%v is a student\n", name) fmt.Printf("%v is %v years old\n", name, age) fmt.Printf("%v has got GPA %v/5 in SSC\n", name, gpa) fmt.Printf("%v originally from %v\n", name, COUNTRY); fmt.Printf("num1 = %v, num2 = %v\n", num1, num2); }
package main
import "fmt"
func main(){
// string formatting
// var name = "Anisul Islam"
// fmt.Printf("%s\n",name)
// fmt.Printf("%q\n",name)
// floating number formatting
// var number = 3.1416
// fmt.Printf("%.2f\n",number)
var decimalNumber int
fmt.Printf("decimal number= ")
fmt.Scanf("%v", &decimalNumber)
fmt.Printf("Binary Number = %b\n",decimalNumber)
fmt.Printf("Octal Number = %o\n",decimalNumber)
fmt.Printf("Hexa Number = %x\n",decimalNumber)
}-
operator - symbol for doing calculation
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Types of operators
- Arithmetic Operators -> +, -, *, /, %
- Assignment Operators -> =, +=, -=, *=, /=, %=
- Unary Operators -> ++, --
- Relational Operators
- Logical operators -> &&, ||, !
- Bitwise operators -> &, |, ^
- others -> , (comma), & (returns address), * (pointer)
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example of Arithmetic operator
package main import "fmt" func main(){ // arithmetic operator -> +, -, *, /, % var num1, num2 int fmt.Printf("num1= "); fmt.Scan(&num1) fmt.Printf("num2= "); fmt.Scan(&num2) result := num1 + num2 fmt.Printf("%v+%v=%v\n", num1, num2, result) result = num1 - num2 fmt.Printf("%v-%v=%v\n", num1, num2, result) result = num1 * num2 fmt.Printf("%v*%v=%v\n", num1, num2, result) var result2 = float32(num1) / float32(num2) fmt.Printf("%v/%v=%v\n", num1, num2, result2) result = num1 % num2 fmt.Printf("%v%%%v=%v\n", num1, num2, result) }
package main
import "fmt"
func main(){
var radius, area float32
fmt.Printf("Enter Radius : ")
fmt.Scan(&radius)
area = 3.1416 * radius * radius
fmt.Printf("Area of circle: %v\n",area)
// a program to calculate area of triangle
// var base, height, area float32
// fmt.Printf("Base = ")
// fmt.Scan(&base)
// fmt.Printf("Height = ")
// fmt.Scan(&height)
// area = 0.5 * base * height
// fmt.Printf("Area of triangle = %v\n", area)
} package main
import "fmt"
func main(){
// 2. Assignment Operators -> =, +=, -=, *=, /=, %=
x := 4
x = x + 1
x+=1 // x = x + 1
x-=1 // x = x - 1
x*=1 // x = x * 1
x/=1 // x = x / 1
x%=1 // x = x % 1
fmt.Printf("x = %v\n",x)
} package main
import "fmt"
func main(){
x := 18 // 18 = 10010
y := 17 // 17 = 10001
and := x & y //16 = 10000
or := x | y //19 = 10011
exor := x ^ y //3 = 00011
fmt.Printf("x & y = %v\n",and)
fmt.Printf("x | y = %v\n",or)
fmt.Printf("x ^ y = %v\n",exor)
} // with if only
package main
import "fmt"
func main(){
// a program to determine positive / negative / zero
number := 10
if number > 0 {
fmt.Printf("Positive\n")
}
if number < 0 {
fmt.Printf("Negative\n")
}
if number == 0 {
fmt.Printf("Zero\n")
}
}
// with if, else if
package main
import "fmt"
func main(){
// a program to determine positive / negative / zero
number := 10
if number > 0 {
fmt.Printf("Positive\n")
} else if number < 0 {
fmt.Printf("Negative\n")
} else if number == 0 {
fmt.Printf("Zero\n")
}
}
// with if, else if, else
package main
import "fmt"
func main(){
// a program to determine positive / negative / zero
number := 10
if number > 0 {
fmt.Printf("Positive\n")
} else if number < 0 {
fmt.Printf("Negative\n")
} else {
fmt.Printf("Zero\n")
}
} // a go program to determine even/odd
package main
import "fmt"
func main(){
var number int
fmt.Printf("Enter any integer: ")
fmt.Scanf("%v",&number)
if number % 2 == 0 {
fmt.Printf("Even\n")
} else {
fmt.Printf("Odd\n")
}
}package main
import "fmt"
func main(){
var number1, number2, number3 int
fmt.Printf("Enter 3 numbers: ")
fmt.Scanf("%v %v %v",&number1, &number2, &number3)
if number1 > number2 {
if number1 > number3 {
fmt.Printf("%v is the largest number\n", number1)
}else{
fmt.Printf("%v is the largest number\n", number3)
}
} else if number2 > number1 {
if number2 > number3 {
fmt.Printf("%v is the largest number\n", number2)
}else{
fmt.Printf("%v is the largest number\n", number3)
}
} else {
fmt.Printf("Numbers are equal\n")
}
}package main
import "fmt"
func main(){
var number1, number2, number3 int
fmt.Printf("Enter 3 numbers: ")
fmt.Scanf("%v %v %v",&number1, &number2, &number3)
if (number1 > number2) && (number1 > number3){
fmt.Printf("%v is the largest number\n", number1)
} else if (number2 > number1) && (number2 > number3){
fmt.Printf("%v is the largest number\n", number2)
} else if (number3 > number1) && (number3 > number2){
fmt.Printf("%v is the largest number\n", number3)
} else {
fmt.Printf("Numbers are equal\n")
}
} // a go program to spell digits with if, else if, else
package main
import "fmt"
func main(){
var digit int
fmt.Printf("Enter a digit (0-9): ")
fmt.Scanf("%v",&digit)
if (digit == 0){
fmt.Printf("Zero\n")
} else if (digit == 1){
fmt.Printf("One\n")
} else if (digit == 2){
fmt.Printf("Two\n")
} else if (digit == 3){
fmt.Printf("Three\n")
} else if (digit == 4){
fmt.Printf("Four\n")
} else if (digit == 5){
fmt.Printf("Five\n")
} else if (digit == 6){
fmt.Printf("Six\n")
} else if (digit == 7){
fmt.Printf("Seven\n")
} else if (digit == 8){
fmt.Printf("Eight\n")
} else if (digit == 9){
fmt.Printf("Nine\n")
} else {
fmt.Printf("Not a digit\n")
}
} // a go program to spell digits with switch statement
package main
import "fmt"
func main(){
var digit int
fmt.Printf("Enter a digit (0-9): ")
fmt.Scanf("%v",&digit)
switch digit {
case 0:
fmt.Printf("Zero\n")
case 1:
fmt.Printf("One\n")
case 2:
fmt.Printf("Two\n")
case 3:
fmt.Printf("Three\n")
case 4:
fmt.Printf("Four\n")
case 5:
fmt.Printf("Five\n")
case 6:
fmt.Printf("Six\n")
case 7:
fmt.Printf("Seven\n")
case 8:
fmt.Printf("Eight\n")
case 9:
fmt.Printf("Nine\n")
// multiple cases possible
// case 0,1,2,3,4:
// fmt.Printf("less than 5" )
default:
fmt.Printf("Not a digit\n")
}
}- in go we have only 1 loop which is for loop; can take form of while loop as weell
- it helps us to execute some statements again and again
package main
import "fmt"
func main(){
// series -> 2 + 4 + 6 + 8 + ... N
var startNumber, endNumber int
fmt.Printf("Enter the starting number of series: ")
fmt.Scan(&startNumber)
fmt.Printf("Enter the last number of series: ")
fmt.Scan(&endNumber)
sum := 0
for i := startNumber; i <= endNumber; i=i+2 {
sum = sum + i
}
fmt.Printf("sum = %v\n",sum)
} package main
import "fmt"
func main(){
// break, continue statement
for i := 1; i <= 10; i++ {
if i%2 == 0 {
continue
}
fmt.Printf("%v\n",i)
}
for i := 1; i <= 10; i++ {
if i%2 == 0 {
break
}
fmt.Printf("%v\n",i)
}
} package main
import "fmt"
func square (number int) int{
return number * number
}
func displayMessage(country string){
fmt.Printf("I love my motherland: %v\n", country)
}
func main(){
displayMessage("Bangladesh")
displayMessage("India")
fmt.Printf("Square of 6 = %v\n",square(6))
fmt.Printf("Square of 7 = %v\n",square(7))
} package main
import "fmt"
func add(x, y float32) float32{
return x + y
}
func sub(x, y float32) float32{
return x - y
}
func mul(x, y float32) float32{
return x * y
}
func div(x, y float32) float32{
return x / y
}
func main(){
var num1, num2, result float32
var option string
i:=true
for i==true {
fmt.Printf("num1 = ")
fmt.Scan(&num1)
fmt.Printf("num2 = ")
fmt.Scan(&num2)
fmt.Printf("choose an option ( + - * / ) : ")
fmt.Scan(&option)
switch option {
case "+":
result = add(num1, num2)
case "-":
result = sub(num1, num2)
case "*":
result = mul(num1, num2)
case "/":
result = div(num1, num2)
default:
fmt.Println("Invalid option")
continue;
}
fmt.Printf("Result = %v\n",result)
}
}-
dereferencing operator
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A pointer is a variable whose value is the address of another variable, declaration: var varName *varType
package main import "fmt" func change (val int) { val = 8 } func changeWihPointer (val *int) { *val = 8 } func main(){ x:=10 change(x) fmt.Println(x) // call by reference changeWihPointer(&x) fmt.Println(x) }
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example
package main import "fmt" type Student struct{ name string age int id int } func main(){ <!-- type Student struct{ name string age int id int } --> rahim := Student{"Anisul", 32,1302020017} rahim.age = 30 fmt.Println(rahim) fmt.Println(rahim.id) fmt.Println(rahim.name) fmt.Println(rahim.age) } // passing struct in a function package main import "fmt" type Student struct { name string age int id int } func displayInfo(s Student) { fmt.Println(s.name) fmt.Println(s.age) } func main() { s1 := Student{"Anisul", 32, 1302020017} displayInfo(s1) } // if we need to change data package main import "fmt" type Student struct { name string age int id int } func (x *Student) increaseAge(val int) { x.age += val } func main() { s1 := Student{"Anisul Islam", 32} s1.increaseAge(1) fmt.Println(s1.age) } // timer app // Employee management app
- array is fixed in Go
- var arrayName[size] dataType
- only the same data type in one array
- var array_name = [length]datatype{values} // here length is defined
- array index starts with 0
- what if we dont know the size of array then we will use slice; allows us to use dynamic size
- append(sliceName, sliceNewValue)