if / else

// Basic if
if condition {
	// Executes when condition is true
}

// if-else
if condition {
	// Executes when true
} else {
	// Executes when false
}

// if-else if-else
if condition1 {
	// Executes when condition1 is true
} else if condition2 {
	// Executes when condition2 is true
} else {
	// Executes when neither condition is true
}

// if with initialization statement (variable scope is limited to the if block)
if initStatement; condition {
	// Variables declared in initStatement are only valid here
}

package main

import (
	"fmt"
	"strconv"
)

func grade(score int) string {
	if score >= 90 {
		return "A"
	} else if score >= 70 {
		return "B"
	} else if score >= 50 {
		return "C"
	} else {
		return "D"
	}
}

func main() {
	fmt.Println(grade(95)) // A
	fmt.Println(grade(72)) // B
	fmt.Println(grade(40)) // D

	// if with initialization statement (idiomatic error handling pattern)
	if n, err := strconv.Atoi("42"); err == nil {
		fmt.Printf("Conversion succeeded: %d\n", n) // n is only valid here
	} else {
		fmt.Println("Conversion failed:", err)
	}

	// Example of a failed conversion
	if n, err := strconv.Atoi("abc"); err == nil {
		fmt.Println(n)
	} else {
		fmt.Println("Error:", err)
	}

	// Map value lookup with if (idiomatic pattern)
	m := map[string]int{"alice": 100, "bob": 80}
	if score, ok := m["alice"]; ok {
		fmt.Println("alice's score:", score)
	}
}

The if statement with an initialization (e.g., if v, err := f(); err == nil { ... }) is one of the most common patterns in Go. It lets you receive return values from a function and check a condition at the same time, while keeping the variable scope limited to the if block.

In Go, adding parentheses around the condition is not a syntax error, but gofmt (the official formatter) will automatically remove them. Follow Go's code style and write conditions without parentheses.

Go does not have a ternary operator (condition ? A : B). Assign values conditionally using a regular if-else statement instead. If you have many branches, consider using a switch statement for better readability.