Go Language

Learn Go: Golang Control Flow Statements: If, If-Else #8

In this tutorial you'll learn how to write decision-making conditional statements used to perform different actions in Golang.

Lets go!!

Published · Jan 15 2020

Previous Tutorial: Understanding Scope Rules in Golang #7

If statements are used to specify whether a block of code should be executed or not depending on a given condition.

If Statement
Following is the syntax of if statements in Golang -
if(condition) {
  // Code to be executed if the condition is true.
}

Here is a simple example -
package main
import "fmt"

func main() {
	var x = 25
	if(x % 5 == 0) {
		fmt.Printf("%d is a multiple of 5\n", x)
	}
}

https://play.golang.org/p/4MO0Fl9fkJT

Note that, You can omit the parentheses () from an if statement in Golang, but the curly braces {} are mandatory -
var y = -1
if y < 0 {
	fmt.Printf("%d is negative\n", y)
}

You can combine multiple conditions using short circuit operators && and || like so -
var age = 21
if age >= 17 && age <= 30 {
	fmt.Println("My Age is between 17 and 30")
}	

. . .

If-Else Statement
An if statement can be combined with an else block. The else block is executed if the condition specified in the if statement is false -
if condition {
  // code to be executed if the condition is true
} else {
  // code to be executed if the condition is false
}


Here is a simple example -
package main
import "fmt"

func main() {
	var age = 18
	if age >= 18 {
		fmt.Println("You're eligible to vote!")
	} else {
		fmt.Println("You're not eligible to vote!")
	}
}

https://play.golang.org/p/-c6az2f9no4
. . .
If-Else-If Chain
if statements can also have multiple else if parts making a chain of conditions like this -
package main
import "fmt"

func main() {
	var BMI = 21.0
	if BMI < 18.5 {
		fmt.Println("You are underweight");
	} else if BMI >= 18.5 && BMI < 25.0 {
		fmt.Println("Your weight is normal");
	} else if BMI >= 25.0 && BMI < 30.0 {
		fmt.Println("You're overweight")
	} else {
		fmt.Println("You're obese")
	}
}

https://play.golang.org/p/EJAEamziBHh
. . .
If with a short statement
An if statement in Golang can also contain a short declaration statement preceding the conditional expression -
if n := 10; n%2 == 0 {
  fmt.Printf("%d is even\n", n)
} 

The variable declared in the short statement is only available inside the if block and it’s else or else-if branches -
if n := 15; n%2 == 0 {
  fmt.Printf("%d is even\n", n)
} else {
  fmt.Printf("%d is odd\n", n)
}

Note that, If you’re using a short statement, then you can’t use parentheses. So the following code will generate a syntax error -
// You can't use parentheses when `if` contains a short statement
if (n := 15; n%2 == 0) { // Syntax Error

}
. . .
Conclusion
That’s all folks. In this article, you learned how to work with control flow statements like if, if-else  in Golang.

In the next article, You’ll learn how to define functions in Go. See you in the next post!
. . .
Next Tutorial:  Golang Control Flow Statements: for loops #9

Golang Tutorial Series:  Learn Go: Beginners Guide to Learn Golang from Scratch!
. . .

References: 
[ 1 ] Golang Control Flow Statements: If-else