Go : How Go handles error handling

Error handling is an important aspect of programming, and Go provides several mechanisms for handling errors. In Go, errors are represented as values of the built-in error type, which is an interface that defines a single method:

type error interface {
    Error() string
}

The Error method returns a string that describes the error. When an error occurs in a Go program, it can return an instance of the error type that describes the error.

Go’s approach to error handling is different from many other programming languages in that it does not use exceptions for error handling. Instead, Go uses multiple return values to indicate the success or failure of a function. When a function returns an error value, it is the responsibility of the caller to check the error value and handle the error if necessary.

For example, consider the following function that reads a file and returns the contents as a string:

func readFile(filename string) (string, error) {
    contents, err := ioutil.ReadFile(filename)
    if err != nil {
        return "", err
    }
    return string(contents), nil
}

In this example, the readFile function returns two values: a string that contains the contents of the file and an error value. If there is an error reading the file, the error value will be non-nil, and the caller should check for this error and handle it appropriately.

To handle errors, Go provides a common idiom for checking for error values and returning early if an error occurs:

contents, err := readFile("file.txt")
if err != nil {
    log.Fatalf("Error reading file: %v", err)
}

In this example, the readFile function is called and its two return values are assigned to the contents and err variables. If the err variable is non-nil, the program logs an error message and exits.

Go’s approach to error handling encourages programmers to explicitly handle errors rather than relying on exceptions. This makes it easier to reason about the behavior of a program, since it is clear what the program will do in the presence of errors. Additionally, Go’s approach to error handling can result in more efficient and readable code, since error handling logic can be kept close to the source of the error, rather than being scattered throughout the code.