Go - return Keyword Examples

Return. In Go programs the return keyword is used in all methods (except when omitted in ones that return no values). It is possible to return multiple values at once in this language.

func

With named return values, we can assign to these names to indicate what values we are returning. A return statement is still needed to exit the method.

Example. This Go program uses the return statement in 5 separate funcs. The funcs return zero, 1, or more than 1 value in different ways.

Part 1 It is possible to return a single value from a Go function. The value is specified after the return keyword.

Part 2 If a function returns no value, we can use the return keyword with no argument—or omit return entirely at the method's end.

Part 3 Often a function returns multiple values, and these values have no names. We can return them with a single return statement.

Part 4 For functions with named return values, we can assign to those names and then return—the return statement can be used on its own.

Part 5 If a function has one unnamed return value, we can omit assigning to it. The default value is used.

package main

import "fmt"

// Part 1: can return a single value from a function.
func Example1() int {
    return 10
}

// Part 2: can return no value (void method).
func Example2() {
    fmt.Println("Inside Example2")
    return
}

// Part 3: can return multiple values that are not named.
func Example3() (string, int) {
    return "bird", 10
}

// Part 4: can return multiple named values.
func Example4() (name string, count int) {
    name = "bird"
    count = 10
    return
}

// Part 5: only the named return values need to be assigned.
func Example5() (name string, _ int) {
    name = "bird"
    return
}

func main() {
    // Invoke the example methods.
    result := Example1()
    fmt.Println("Example1", result)

    Example2()

    name, count := Example3()
    fmt.Println("Example3", name, count)

    name, count = Example4()
    fmt.Println("Example4", name, count)

    name, count = Example5()
    fmt.Println("Example5", name, count)
}Example1 10
Inside Example2
Example3 bird 10
Example4 bird 10
Example5 bird 0

Return, loop. It is possible to end a for-loop with a break, but often it is possible to use a return instead. This can make the method easier to read—we do not need to look for more statements.

break

Part 1 We create a slice that have 4 integers in it—the value 30 is the third element in the slice.

Slice

Part 2 We use a for-range loop over the elements in the slice, and if an element is greater than or equal to 30, we return. This ends the loop.

for

package main

import "fmt"

func Example() {
    // Part 1: use some integers in a slice.
    numbers := []int{10, 20, 30, 40}
    // Part 2: loop over the integers, and if we are greater or equal to 30, return.
    for _, n := range numbers {
        if n >= 30 {
            return
        }
        fmt.Println(n)
    }
}

func main() {
    Example()
}10
20

Summary. With the return keyword, we can return multiple values. Often Go programs will return a bool value that tells the caller whether the function succeeded in its task.