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Functions and errors

Define functions with func, return several values, and return an error instead of throwing.

Runs in Zerethon IDE · Go 1.27 Official Go documentation ↗
main.go 
package main

import (
	"errors"
	"fmt"
)

func greet(name string) string {
	return "Hello, " + name + "!"
}

func stats(numbers []int) (int, int, float64) {
	low, high, sum := numbers[0], numbers[0], 0
	for _, n := range numbers {
		low = min(low, n)
		high = max(high, n)
		sum += n
	}
	return low, high, float64(sum) / float64(len(numbers))
}

func divide(a, b int) (int, error) {
	if b == 0 {
		return 0, errors.New("division by zero")
	}
	return a / b, nil
}

func main() {
	fmt.Println(greet("Ada"))
	low, high, mean := stats([]int{4, 8, 6})
	fmt.Println(low, high, mean)

	if _, err := divide(1, 0); err != nil {
		fmt.Println("error:", err)
	}
	q, _ := divide(9, 3)
	fmt.Println(q)

	square := func(x int) int { return x * x }
	fmt.Println(square(9))
}

Output

Hello, Ada!
4 8 6
error: division by zero
3
81
  • The type comes after the name: func divide(a, b int) (int, error).
  • Go has no exceptions. A function that can fail returns an error as its last value; the caller checks if err != nil.
  • _ throws a value away. You must take or discard every returned value you assign.
  • min and max are built in since Go 1.21.

Tip: Wrap an error with context using fmt.Errorf("reading %s: %w", name, err); errors.Is and errors.As find the original later.

Related topics

Official references