Go — Switch

Basic switch

package main

import "fmt"

func main() {
    day := "Monday"

    switch day {
    case "Monday":
        fmt.Println("Start of week")
    case "Friday":
        fmt.Println("Almost weekend")
    case "Saturday", "Sunday":
        fmt.Println("Weekend!")
    default:
        fmt.Println("Midweek")
    }
}

Expression-less switch

score := 85

switch {
case score >= 90:
    fmt.Println("A")
case score >= 80:
    fmt.Println("B")
case score >= 70:
    fmt.Println("C")
default:
    fmt.Println("F")
}

Switch with init statement

switch status := getStatus(); {
case status == 200:
    fmt.Println("OK")
case status == 404:
    fmt.Println("Not Found")
case status >= 500:
    fmt.Println("Server Error")
}

Type switch

var x interface{} = "hello"

switch v := x.(type) {
case int:
    fmt.Printf("Integer: %d\n", v)
case string:
    fmt.Printf("String: %s\n", v)
case bool:
    fmt.Printf("Boolean: %t\n", v)
default:
    fmt.Printf("Unknown: %T\n", v)
}

fallthrough

n := 2

switch n {
case 1:
    fmt.Println("One")
    fallthrough
case 2:
    fmt.Println("Two")
    fallthrough
case 3:
    fmt.Println("Three")
}
// Output: Two Three

Multiple cases

char := 'a'

switch char {
case 'a', 'e', 'i', 'o', 'u':
    fmt.Println("Vowel")
default:
    fmt.Println("Consonant")
}

Switch with channels

ch := make(chan int, 1)
ch <- 42

select {
case v := <-ch:
    fmt.Println("Received:", v)
default:
    fmt.Println("No value")
}

Best practices

• Use switch over long if-else if chains
• Avoid fallthrough — it's rarely needed
• Use expression-less switch for range-based logic
• Use select for channel operations

Mini Practice

Write Go code that:

1. Uses switch to classify a number range
2. Uses type switch on an interface{}
3. Uses fallthrough intentionally
4. Combines multiple cases in one case clause

Up Next

In the next lesson, you'll learn about Loops — Go's only loop construct.