Flow control

if/else

Branching with if and else is same as in other languages. The if statement is used to execute a block of code if a condition is true. The else statement can be used to execute a block of code if the condition is false. There is also else if for multiple conditions.

package main
import "fmt"

func main() {
  if true {
      fmt.Println("Condition is true")
  } else {
      fmt.Println("Condition is false")
  }
}

    
    a := 10
    if a > 5 {
        fmt.Println("a is greater than 5")
    } else if a < 5 {
        fmt.Println("a is less than 5")
    } else {
        fmt.Println("a is equal to 5")
    }
    

inline

You can also use if in a inline value assignment. This is useful when you want to declare a variable and check its value in the same line.

    if a := 10; a > 5 {
        fmt.Println("a is greater than 5")
    } else {
        fmt.Println("a is less than or equal to 5")
    }

In more complex cases, this is useful to getting the value of some function without having to declare a variable outside the scope of the if statement.

    if ok := someFunction(); !ok {
        fmt.Println("It's not ok")
    }

loop

Loop or iteration is done with for statement. The for statement can be used to iterate over a range of values, such as an array or a slice. It can also be used to create an infinite loop.

package main

import "fmt"

func main() {
  for i := 0; i < 5; i++ {
      fmt.Println(i)
  }
}

Assuming that you've declared an array or slice, you can use either looping as above or using range. The difference is if you opt for using range, you can get the index and value of the element in the array or slice. While using for as above, you can only get the index.

package main

import "fmt"

func main() {
  arr := []int{100, 90, 80, 70, 60}

  fmt.Println("Using for loop:")
  for i := 0; i < len(arr); i++ {
      fmt.Println(i, arr[i])
  }

  fmt.Println("Using range:")
  for i, v := range arr {
      fmt.Println(i, v)
  }
}

while loop equivalent

It is common in other languages to use while loop. But there is no while loop in Go. You can use for statement to create a while loop.

    i := 0
    for i < 5 {
        fmt.Println(i)
        i++
    }

Just beware if you use for statement without any condition, it will create an infinite loop.

    for {
        fmt.Println("This is an infinite loop that never ends 🧞")
    }

switch

Switch statements in Go are similar to other languages. The switch statement allows you to execute different blocks of code based on the value of a variable.

package main

import "fmt"

func main() {
    day := 3
    switch day {
    case 1:
        fmt.Println("Monday")
    case 2:
        fmt.Println("Tuesday")
    case 3:
        fmt.Println("Wednesday")
    default:
        fmt.Println("Unknown day")
    }
}

defer

The defer statement is rather unique to Go. It is used to schedule a function call to be executed after the function completes. The defer statement is executed in LIFO (Last In First Out) order, which means that the last deferred function will be executed. This is useful for cleaning up resources, such as closing files or network connections. I swear that you will use this a lot in your code 🤞.

package main

import "fmt"

func main() {
  defer fmt.Println("Deferred call")
  fmt.Println("Regular call")
}

The pyramid

The pyramid problem is a common learning exercise in programming, especially when it comes to flow control. The goal is to print a pyramid of numbers. The pyramid has a certain number of rows, and each row contains a certain number of numbers. Asterisks are printed in a pyramid shape, with the first row containing one number, the second row containing two numbers, and so on.

     *
    ***
   *****
  *******
 *********