Control Flow

Go provides a small, powerful set of control flow statements: if/else, switch, for, and defer. Unlike many languages, Go has only one loop construct — the for loop — which covers all looping patterns.

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If / Else

Basic If

if x > 10 {
    fmt.Println("x is greater than 10")
}

Note: no parentheses around the condition, but braces are required.

If / Else

if x > 10 {
    fmt.Println("big")
} else if x > 5 {
    fmt.Println("medium")
} else {
    fmt.Println("small")
}

If with Init Statement

Go allows a short statement before the condition — perfect for error handling:

if err := doSomething(); err != nil {
    fmt.Println("Error:", err)
    return
}
// err is not accessible here — scoped to the if block

This pattern is extremely common in Go. The variable declared in the init statement is scoped to the if/else block.

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Switch

Go's switch is more powerful than in many other languages:

Basic Switch

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

Key Differences from C/Java

Feature	Go	C / Java
Automatic break	Yes — each case breaks automatically	No — must add break explicitly
Fallthrough	Explicit with fallthrough keyword	Default behaviour
Multiple values	case "a", "b":	Requires fallthrough
Expressions	Cases can be expressions, not just constants	Constants only (Java: limited)

Switch with No Condition

A switch with no condition is equivalent to if/else if/else:

switch {
case score >= 90:
    grade = "A"
case score >= 80:
    grade = "B"
case score >= 70:
    grade = "C"
default:
    grade = "F"
}

Switch with Init Statement

Like if, switch supports an init statement:

switch os := runtime.GOOS; os {
case "linux":
    fmt.Println("Linux")
case "darwin":
    fmt.Println("macOS")
default:
    fmt.Println(os)
}

Type Switch

A type switch tests the type of an interface value:

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

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For Loops

Go has only one loop construct: for. It replaces while, do-while, and for loops from other languages.

Classic For Loop

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

While-Style Loop

for x < 100 {
    x *= 2
}

Infinite Loop

for {
    // runs forever (use break or return to exit)
    if done {
        break
    }
}

Range Loop

range iterates over slices, arrays, maps, strings, and channels: