Error handling

In Go Errors are values just like any other return value from a function. There NOT considered exceptional, we can expect them right?

For example, the following code used to open a file returns two values, the second being the values of a potential error:

f, err := os.Open("/path/to/file")
if err != nil {
    // Handle error
}
defer f.close()

We consider error handling immediately, and deal with them as soon as they might occur.

This simplifies code review and understanding, this pattern is one of the reasons Go is considered a stable and production ready language.

Mechanics

Don't just check errors, handle them gracefully.

To be an error in go you have a method called Error which returns a string. The error is of the built in type interface.

You can create your own errors:

main.go

package main

import (
    "errors"
    "fmt"
)

func main() {

    err := errors.New("this is an error message")
    fmt.Println(err)

    err2 := fmt.Errorf("this error wraps the first one: %w", err)
    fmt.Println(err2)
}

With these features, we can always handle errors in function, checking and returning an error should one arise.

package main

import (
    "errors"
    "fmt"
    "log"
)

func main() {

    message, err := Message("")

    if err != nil {
        log.Fatal(err)
    }

    fmt.Println(message)
}

func Message(name string) (string, error) {

    if name == "" {
        return "", errors.New("empty name")
    }

    message := fmt.Sprintf("Hi, %v. Welcome!", name)
    return message, nil
}

Panics