Branching

If statements

A simple if statement:

main.go

package main

import "fmt"

func main() {

    height := 180

    if height < 200 {
        fmt.Println("Less than two meters.")
    }

    fmt.Println("After if statement.")
}

With and else statement:

main.go

package main

import "fmt"

func main() {

    height := 200

    if height <= 200 {
        fmt.Println("Less than or equal to two meters.")
    } else {
        fmt.Println("More than two meters.")
    }

    fmt.Println("After if statement.")
}

With multiple if conditions:

main.go

package main

import "fmt"

func main() {

    height := 400

    if height <= 200 {
        fmt.Println("Less than or equal to two meters.")
    } else if height <= 300 {
        fmt.Println("Less than or equal to three meters.")
    } else {
        fmt.Println("More than three meters.")
    }

    fmt.Println("After if statement.")
}

You can include the initializer, for example:

main.go

package main

import "fmt"

func main() {

    if height := 180; height < 200 {
        fmt.Println("Less than two meters.")
    }

    fmt.Println("After if statement.")
}

Switch

Example switch statement:

main.go

package main

import "fmt"

func main() {

    switch id := 1; id {
    case 1:
        fmt.Println("Case one")
    case 2:
        fmt.Println("Case two")
    default:
        fmt.Println("Default case")

    }

    fmt.Println("After switch statement.")
}

Another example which includes an infinite loop which is labeled loop providing a means to break from the for loop:

main.go

package main

import (
    "bufio"
    "fmt"
    "os"
    "strings"
)

func main() {

    userInput := bufio.NewReader(os.Stdin)

loop:
    for {

        fmt.Println("Pick an option:")
        fmt.Println("1) Option one")
        fmt.Println("2) Option two")
        fmt.Println("q) Quit")

        choice, _ := userInput.ReadString('\n')

        switch strings.TrimSpace(choice) {
        case "1":
            fmt.Println("You picked option one")
        case "2":
            fmt.Println("You picked option two")
        case "q":
            break loop
        default:
            fmt.Println("Option unknown")
        }
    }
}

Example fo a logical switch statement, where the condition is looking for true or false.

main.go

package main

import (
    "fmt"
)

func main() {

    switch number := 42; {
    case number < 10:
        fmt.Println("Number is less than ten")
    case number < 50:
        fmt.Println("Number is less than fifty")
    default:
        fmt.Println("Number is fifty or more")
    }
}

Deferred functions

Deferred functions taken advantage of the window between when a function exits and to program returns its focus to the calling point of said function.

A great example of deferred functions are when opening and closing a database connection.

Deferred functions operate with a first-in last-out behavior, when the main() function finishes in the following example, the two deferred functions will execute:

main.go

package main

import (
    "fmt"
)

func main() {

    fmt.Println("Main function 1")

    defer fmt.Println("Deferred function 1")

    fmt.Println("Main function 2")

    defer fmt.Println("Deferred function 2")
}

Output:

Main function 1
Main function 2
Deferred function 2
Deferred function 1

Panic and recovery

Panic and recovery leverage the deferred function.

Example:

main.go

package main

import (
    "fmt"
)

func main() {
    dividend, divisor := 10, 5
    fmt.Printf("%v divided by %v is %v\n", dividend, divisor, divide(dividend, divisor))

    dividend, divisor = 10, 0
    fmt.Printf("%v divided by %v is %v\n", dividend, divisor, divide(dividend, divisor))
}

func divide(dividend, divisor int) int {
    defer func() {
        if message := recover(); message != nil {
            fmt.Println(message)
        }
    }()
    return dividend / divisor
}

Goto statements

It's likely you will never use a goto statement in your go programming. They use labels.

A goto statement can leave a block, that is a block of code between curly braces. You can't jump after variable declarations, else they wouldn't get declared. You can't jump into another code black.