About

Conditionals are statements that execute different code depending on whether a condition is true or false.

An if statement executes its body only when its condition is true. Go has no concept of truthy or falsy values so the condition must be of type bool. Expressions like if mySlice { ... } or if 1 { ... } are compile errors.

func describe(val string) string {
    if val == "val" {
        return "was val"
    }
    return "was not val"
}

Use else if to check additional conditions, and else as a fallback if none match. Conditions are evaluated top to bottom, and only the first branch whose condition is true will run.

number := 0
result := "This number is "

if number > 0 {
    result += "positive"
} else if number < 0 {
    result += "negative"
} else {
    result += "zero"
}

Generally, Go favors returning early from the exceptional case and avoiding else.

func getVal(connected bool) int {
    if !connected {
        return readLocalVal()
    }

    return readVal()
}

An if statement can also include a short initialization statement. This is commonly used to check an error immediately after a call:

num := 7
if v := 2 * num; v > 10 {
    fmt.Println(v)
} else {
    fmt.Println(num)
}
// Output: 14

Variables declared in the initialization statement are only in scope within the entire if/else chain. Notably, Go has no ternary operator, a deliberate design choice to keep code easy to scan.

To learn more, see Go by Example: If/Else.

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Originally from Exercism go concepts