How to handle errors gracefully in Golang

In recent years, Golang has become one of the most popular programming languages ​​today due to its many excellent features and perfect performance. However, whether you are using Golang for web development or other fields, error management is still an unavoidable problem. How to handle errors gracefully in Golang? What experiences and suggestions are there?

1. Error classification
In Golang, errors are placed in the error type. The Error type is defined to contain only one Error method, which returns a string. When an error occurs, a new Error type is usually created. In Golang, you can use the built-in error package or custom errors to represent error messages.

Generally speaking, errors in Golang can be divided into the following three categories:

1. Predefined errors
Predefined errors are built-in error types, usually used to represent errors in Golang System level error. For example, errors such as EOF are encountered during file reading. Most of these errors can be handled using the built-in error functions.

2. Custom errors
Custom errors are designed by programmers when writing code and can generate specific types of errors. For example, errors such as JSON parsing failure. For this type of error, the programmer must define the error type himself and return it when the function is called.

3. Runtime errors
Runtime errors are errors encountered by the Golang interpreter when running the program. For example, division by 0 errors, etc. These errors are usually caused by system-level errors and cannot be predicted, so programmers need to pay attention to handling such errors.

2. Go's error handling method
In Golang, the following two methods are usually used to handle errors:

1. Return value processing
In Golang, usually use Return error information in the value to handle errors. Before a function call, it is common to check whether the return value of other function calls is of the wrong type. If so, terminates the current function call and returns the error to the caller.

For example, the following code handles errors when reading the greeting.txt file. The function readGreeting returns the error err. If an error occurs, the function will return a nil value and the err error type.

func greet() error {
    contents, err := readGreeting("greeting.txt")
    if err != nil {
        return err
    }
    fmt.Printf("Greetings: %s\n", contents)
    return nil
}

func readGreeting(filename string) (string, error) {
    file, err := os.Open(filename)
    if err != nil {
        return "", err
    }
    defer file.Close()

    reader := bufio.NewReader(file)
    greeting, err := reader.ReadString('\n')
    if err != nil {
        return "", err
    }

    return greeting, nil
}

2, panic and recover
Another way to handle errors in Golang is to use panic and recover. When an error occurs and is not caught, it causes the program to crash. However, if a programmer uses panic within a function, it means that an error has occurred. This panic information will be passed out until it is captured by recover.

For example, the following code example implements a simple example of database connection and access, and how to handle failure situations.

func main() {
    conn := openConnection("localhost", "mydb")
    defer closeConnection(conn)

    if err := insertData(conn, "test"); err != nil {
        log.Fatal(err)
    }
}

func openConnection(ip, dbname string) *DB {
    conn, err := openDB(ip, dbname)
    if err != nil {
        panic(err)
    }
    return conn
}

func insertData(db *DB, data string) error {
    if db == nil {
        panic("No database connection!")
    }
    _, err := db.Exec("INSERT INTO data VALUES (?)", data)
    return err
}

func closeConnection(db *DB) {
    if db == nil {
        panic("No database connection!")
    }
    db.Close()
}

func recoverFunction() {
    if r := recover(); r != nil {
        fmt.Println("Recovered", r)
    }
}

3. Some suggestions
In Golang, error handling needs to be completed by programmers themselves. However, some experience and suggestions can help programmers better handle errors:

1. For system-level errors, you can consider using the built-in error types or errors package, which is easy to understand and use.

2. For custom errors, you can define the error types yourself in the program and return these errors with functions carrying necessary parameters.

3. Using the defer keyword can ensure that when you forget to clean up resources when writing code, you can still clean up resources correctly. This is a very convenient way.

4. Be careful when using panic and recover in programs, and try to avoid using them in programs.

In short, error handling is still an issue that needs attention in Golang. Correct error handling can help programmers deal with various errors that occur in the program and improve the reliability and robustness of the program.

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