An article explaining the error handling mechanism in Golang in detail

Golang is an increasingly popular programming language. Its features are simple and easy to learn, and it supports high concurrency. Therefore, it is very popular in fields such as web development and cloud computing. However, error handling is an essential part of writing complex programs. Golang's error handling method is slightly different compared to other programming languages. This article will introduce the error handling mechanism in Golang and provide some practical handling techniques.

1. Error handling mechanism

In Golang, error is a built-in type, which has a simple implementation, usually a return value. So when a function call fails, it returns an error instead of throwing an exception.

The following is a basic example code that returns an error:

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

In the above code, if the value of b is 0, the function will return a new one created with the errors.New() function error and check the return value at the call site.

When calling a function that returns an error, you should check the error value returned by the function, otherwise the program will terminate.

2. Error handling practice

How to handle errors is an important part of writing high-quality software. Here are some ways to apply error handling:

1. Transparent Errors
   Transparent errors refer to passing errors on the call stack in a Golang application so that they are visible in the final result. This approach enables callers to inspect and handle errors so that they know the root cause of the error.

func DoSomething() error {
    // 调用第三方API，返回一个错误
    resp, err := http.Get("https://google.com")
    if err != nil {
        return fmt.Errorf("failed to get response: %w", err) // 透传错误
    }
    // 处理响应
    // …
}

In the above code, the function DoSomething() obtains the response by calling the http.Get() method, and "transparently transmits" the error returned by the method to the superior function. This means that the DoSomething() function does not handle errors, it indirectly returns an error value generated by http.Get(). Doing so helps track down the root cause of the error.

2. Customized errors
   In Golang, error types can be customized, which makes it easier for programmers to define and find specific types of errors.

type MyError struct {
    ErrCode string
    Message string
}

func (e *MyError) Error() string {
    return fmt.Sprintf("[%s] %s", e.ErrCode, e.Message)
}

func DoSomething() error {
    err := &MyError{
        ErrCode: "1000",
        Message: "something went wrong",
    }
    return err
}

In the above code, we customized a new MyError type, which implements the Error() method. By setting specific error codes and error messages, you can accurately describe the cause of the error.

3. Package level error handling
   In Golang, error handling methods can be set at the package level to successfully handle errors for all function calls. This can be achieved by using the init() function and global variables.

var Log *log.Logger

func init() {
    Log = log.New(os.Stdout, "MyApp: ", log.Ldate|log.Ltime|log.Lshortfile)
}

func DoSomething() error {
    // 处理错误
    if err := DoMoreWork(); err != nil {
        Log.Println(fmt.Errorf("failed to do more work: %w", err))
        return err
    }
    return nil
}

In the above code, we use the global variable Log of the log package to record log messages. When handling errors, log to a file and return the error. This approach eliminates logging-like repetitive behavior between function calls.

In short, error handling is an important task in Golang application development. For programmers, either error handling is done well, or the program may not run properly. Therefore, Golang programmers should understand and adopt error handling practices such as pass-through errors, custom errors, and package-level error handling to ensure that their code remains accurate and efficient at all times.

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