Go

Introduction

• From c++ by google c++ author will convert to exe

• go get githublink→ to download pkg and put under folder pkg

• it has main function to run go run filename.go

  package main //-> our package name 
   
  imort "fmt"
   
  import ("fmt","math") //-> to import multiple pkg
   
  func main(){
  	fmt.Println("hello")
  }

Data types

• string, bool, int, byte , float32 ,float64, arrays

• using var keyword and const → to not reassign

• var name string = “d” (if directly assing vaule we don’t need to mention the data type)

• var age = 23

• name := “test” → this kind of declaration we can be only defined inside function

• name,email := “test”,”email”

• Arrays

   var name [2] string 
  name[0] = "1"
   
  name := [2]string("1","2") //size optional
  //slice 
  name := [2]string{"1","2"}
   
  len(name) //-> to get length
   
  name[1:2] //-> slice the array

• Struct

  type Animal struct {
  class string
  age int
  }
   
  var teddy = Animal{ class:"bear",age:14}
  or 
  Animal{"bear",14}
   
  //teddy.age

• Map

   emails :=  make(map[string]string)
   
   := map[stringstring{"key":"value"}
   
  emails["name"]= "key"

Function

function name (params type) returnType {
	cmd..
}
//type is not mandatory
 
name(params)
 
#multiple return vaule
function name (params type) (int,bool..) {
	return 4,true,..
}
 number ,bool := name()
we can also give name for the return type of function like 
 
function name () (number int , ..) -> it is purely for doc
#Error Handling
 

• Arguments are passed as copy use pointer for call by reference

Pointers

package main
 
import "fmt"
 
func main() {
    // Declare a variable
    var num int = 10
    
    // Declare a pointer variable
    var ptr *int
    
    // Assign the address of num to ptr
    ptr = &num
    
    // Access the value through the pointer
    fmt.Println("Value of num:", num)
    fmt.Println("Value of num through pointer:", *ptr)
    
    // Modify the value through the pointer
    *ptr = 20
    fmt.Println("New value of num:", num)
}
 

Conditions

if x<y || cond2  {
	//code
}  else if {
	//code
} else {
	//code
}
 
//switch
color := "red"
 
switch color {
	case "red":
		//code
  case "":
			//code
	default:
		//code
}

Loops

i :=1
for i<=10 {
	//code 
  i++
}
 
for i:=1 i<10;i++ {
 //code
}
 
//using range
ids := []int{33,33}
 
for i,id := range ids {
	
}
 
//range with map
 
for k,v := range map { }
 

Runes

Go’s runes are used to represent single characters. ‘A’ →65 Runes are kept as numeric codes

If you declare a variable without assigning it a value, that variable will contain the zero value

short variable declaration

instead of explicitly declaring the type of the variable and later assigning to it with = , you do both at once using := .

quantity := 4

If the name of a variable, function, or type begins with a capital letter, it is considered exported and can be accessed from packages outside the current one.

Conversions

Only same type can be do math operation float and int cannot to convert

• int(3.0)
• float64(9)

Packages

Go tools look for package code in a special directory (folder) on your computer called the workspace. By default, the workspace is a directory named go in the current user’s home directory.

The workspace directory contains three subdirectories

• bin, which holds compiled binary executable programs.
• pkg, which holds compiled binary package files.
• src, which holds Go source code.

others

Split your application into components written as regular Go interfaces. Don’t fuss with any networking or serialization code. Focus on your business logic. (https://serviceweaver.dev/)

1. Go routine → make threads simple
2. channel