Errors

Go does not use exceptions. Instead, functions return an error value, and the caller checks it. This makes failure handling explicit.

The error type

error is a built-in type. A nil error means success; a non-nil error describes what went wrong.

Returning an error

Use errors.New to create a simple error. Return it alongside the result.

import (
    "errors"
    "fmt"
)

func divide(a, b int) (int, error) {
    if b == 0 {
        return 0, errors.New("cannot divide by zero")
    }
    return a / b, nil
}

Checking errors

The common pattern is if err != nil.

result, err := divide(10, 0)
if err != nil {
    fmt.Println("Error:", err)
} else {
    fmt.Println("Result:", result)
}

Formatting errors

fmt.Errorf builds an error with formatted text.

name := "config.txt"
err := fmt.Errorf("could not open %s", name)
fmt.Println(err) // could not open config.txt

Checking errors right where they happen keeps Go programs predictable and robust.