Control Structures in Go

Control structures direct the flow of program execution. Go provides several control structures that are clean and easy to use.

If Statements

Basic If Statement

if x > 0 {
    fmt.Println("x is positive")
}

If-Else Statement

if x > 0 {
    fmt.Println("x is positive")
} else {
    fmt.Println("x is non-positive")
}

If with a Short Statement

if value := getValue(); value < 10 {
    fmt.Println("Value is less than 10")
} else {
    fmt.Println("Value is 10 or greater")
}

For Loops

Go has only one looping construct: the for loop. However, it’s very flexible.

Basic For Loop

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

While-Style For Loop

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

Infinite Loop

for {
    fmt.Println("This will run forever")
    // Use break to exit
}

For-Range Loop

numbers := []int{1, 2, 3, 4, 5}
for index, value := range numbers {
    fmt.Printf("Index: %d, Value: %d\n", index, value)
}

Switch Statements

Basic Switch

switch day {
case "Monday":
    fmt.Println("Start of work week")
case "Friday":
    fmt.Println("End of work week")
default:
    fmt.Println("Regular day")
}

Switch with Multiple Cases

switch day {
case "Monday", "Tuesday", "Wednesday", "Thursday", "Friday":
    fmt.Println("Weekday")
case "Saturday", "Sunday":
    fmt.Println("Weekend")
}

Switch without Expression

switch {
case hour < 12:
    fmt.Println("Good morning")
case hour < 17:
    fmt.Println("Good afternoon")
default:
    fmt.Println("Good evening")
}

Break and Continue

Break Statement

Exits the innermost loop or switch statement

for i := 0; i < 10; i++ {
    if i == 5 {
        break
    }
    fmt.Println(i)
}

Continue Statement

Skips to the next iteration of the loop

for i := 0; i < 5; i++ {
    if i == 2 {
        continue
    }
    fmt.Println(i)
}

Practical Example

Here’s a program that combines various control structures:

package main

import "fmt"

func main() {
    // Array of scores
    scores := []int{85, 93, 77, 65, 99, 55}

    for i, score := range scores {
        fmt.Printf("Processing score %d: ", score)

        if score < 60 {
            fmt.Println("Failed")
            continue
        }

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

        if i == len(scores)-1 {
            fmt.Println("Finished processing all scores")
            break
        }
    }
}

Best Practices

Keep conditions simple and readable
Use early returns when possible
Prefer for-range when iterating over collections
Use switch statements instead of long if-else chains
Always use braces, even for single-line blocks

In the next post, we’ll explore Functions in Go, including how to define them, return values, and function types!