Basics of Go (Golang)

1. Go Syntax & Structure

Hello World

package main  // Declares the package (main is the entry point)

import "fmt"  // Import the "fmt" package for input/output

func main() {
  fmt.Println("Hello, World!")  // Prints to the console
}

• Key Points:
  • Every Go file starts with package <name>. Use package main for executable programs.
  • func main() is the entry point of the program.
  • Use import to include external packages (like fmt for formatting).

2. Variables & Data Types

Variable Declaration

var name string = "Alice"  // Explicit type declaration
age := 25                  // Type inferred (short declaration, only inside functions)
pi := 3.14                 // Type inferred as float64
isStudent := true          // Boolean

• Data Types:
  • Basic types: string, int, float64, bool.
  • Zero values: Uninitialized variables default to 0, "", false, etc.

3. Control Structures

If/Else

temperature := 30
if temperature > 28 {
  fmt.Println("It's hot!")
} else if temperature < 10 {
  fmt.Println("It's cold!")
} else {
  fmt.Println("It's pleasant.")
}

For Loop (Go has no while keyword)

// Classic for loop
for i := 0; i < 5; i++ {
  fmt.Println(i)
}

// While-like loop
count := 0
for count < 3 {
  fmt.Println(count)
  count++
}

Switch

day := "Monday"
switch day {
case "Monday":
  fmt.Println("Workday")
case "Saturday", "Sunday":
  fmt.Println("Weekend")
default:
  fmt.Println("Midweek")
}

4. Functions

Basic Function

func add(a int, b int) int {
  return a + b
}

result := add(3, 5)  // result = 8

Multiple Return Values

func divide(a, b float64) (float64, error) {
  if b == 0 {
    return 0, fmt.Errorf("cannot divide by zero")
  }
  return a / b, nil
}

quotient, err := divide(10, 2)  // Handle the error

5. Packages & Imports

• Custom Package:
  • Create a file math/math.go:

  • package math  // Declare the package name
    
    func Multiply(a, b int) int {
      return a * b
    }

  • Use it in main.go:

  • import "your-module-name/math"  // Replace with your module name
    
    func main() {
      product := math.Multiply(4, 5)  // 20
    }

6. Error Handling

Go uses explicit error returns (no exceptions):

file, err := os.Open("data.txt")
if err != nil {
  log.Fatal(err)  // Handle the error
}
defer file.Close()  // Ensure the file closes when the function exits

Summary of Key Concepts

1. Syntax: package, import, func, {} for code blocks.
2. Variables: Use var or := (short declaration).
3. Control Structures: if, for (no while), switch.
4. Functions: Can return multiple values, including errors.
5. Packages: Organize code into reusable modules.