Control Flow

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Examples in Go
If Then Else in Go
by yhuang Go fmt.Println fmt
There is no ternary if in Go, so you’ll need to use a full if statement even for basic conditions.
package main

import "fmt"

func main() {

    if 7%2 == 0 {
        fmt.Println("7 is even")
    } else {
        fmt.Println("7 is odd")
    }

    if 8%4 == 0 {
        fmt.Println("8 is divisible by 4")
    }

    if num := 9; num < 0 {
        fmt.Println(num, "is negative")
    } else if num < 10 {
        fmt.Println(num, "has 1 digit")
    } else {
        fmt.Println(num, "has multiple digits")
    }
}
Last Run  :
7 is odd
8 is divisible by 4
9 has 1 digit
Go "for" loop
by yhuang Go fmt.Println fmt
for is Go’s only looping construct. Here are three basic types of for loops.
package main

import "fmt"

func main() {

    i := 1
    for i <= 3 {
        fmt.Println(i)
        i = i + 1
    }

    for j := 7; j <= 9; j++ {
        fmt.Println(j)
    }

    for {
        fmt.Println("loop")
        break
    }

    for n := 0; n <= 5; n++ {
        if n%2 == 0 {
            continue
        }
        fmt.Println(n)
    }
}
Matching in Go
by yhuang Go fmt.Println time.Now fmt fmt.Print fmt.Printf
case blocks in go automatically break after their branch is executed and the user must use the "fallthrough" keyword to have it continue to match other case blocks.
package main

import (
    "fmt"
    "time"
)

func main() {

    i := 2
    fmt.Print("Write ", i, " as ")
    switch i {
    case 1:
        fmt.Println("one")
    case 2:
        fmt.Println("two")
    case 3:
        fmt.Println("three")
    }

    switch time.Now().Weekday() {
    case time.Saturday, time.Sunday:
        fmt.Println("It's the weekend")
    default:
        fmt.Println("It's a weekday")
    }

    t := time.Now()
    switch {
    case t.Hour() < 12:
        fmt.Println("It's before noon")
    default:
        fmt.Println("It's after noon")
    }

    whatAmI := func(i interface{}) {
        switch t := i.(type) {
        case bool:
            fmt.Println("I'm a bool")
        case int:
            fmt.Println("I'm an int")
        default:
            fmt.Printf("Don't know type %T\n", t)
        }
    }
    whatAmI(true)
    whatAmI(1)
    whatAmI("hey")
}
Go's defer
by yhuang Go fmt.Println os.File fmt fmt.Fprintf fmt.Fprintln
Defer is used to ensure that a function call is performed later in a program’s execution, usually for purposes of cleanup. defer is often used where e.g. ensure and finally would be used in other languages.
package main

import (
    "fmt"
    "os"
)

func main() {

    // Immediately after getting a file object with createFile, we defer the closing of that file with closeFile.
    // This will be executed at the end of the enclosing function (main), after writeFile has finished.
    f := createFile("/tmp/defer.txt")
    defer closeFile(f)
    writeFile(f)
}

func createFile(p string) *os.File {
    fmt.Println("creating")
    f, err := os.Create(p)
    if err != nil {
        panic(err)
    }
    return f
}

func writeFile(f *os.File) {
    fmt.Println("writing")
    fmt.Fprintln(f, "data")

}

func closeFile(f *os.File) {
    fmt.Println("closing")
    err := f.Close()

    if err != nil {
        fmt.Fprintf(os.Stderr, "error: %v\n", err)
        os.Exit(1)
    }
}