How to handle exceptions in golang

Go language is a statically typed programming language that supports object-oriented programming. Compared with other programming languages, its exact name should be "Go" rather than "golang". Go language started in 2007 and is an open source language developed by Google.

In the Go language, exceptions are called "panic" and are not like the exception and capture mechanisms in Java or C#. If an exception occurs, it will cause the program to terminate and print out the corresponding error message stack.

In Go, exception handling is generally not used. Instead, functions are used to return error codes to handle exceptions. This approach is called error handling. Error handling is a very important mechanism for the Go language.

In the Go language, the function can return an additional error type value, indicating the execution status of the function. The value of this error value can be nil, indicating that the function execution is successful, otherwise it indicates that the execution failed. If a function's error return value is handled, the return result can be inspected for errors and efficient and detailed error reporting can be provided. This error handling mechanism makes the Go language ideal for writing highly reliable code.

Normally, we handle error information by returning error in the function. The specific approach is that when an error is found, we will set the value of error to a non-nil value and record the contextual information about the error. For other types of error conditions, it can also be handled by returning error.

For example, as follows:

func foo() error {
    if _, err := os.Stat("my_file"); err != nil {
        if os.IsNotExist(err) {
            return fmt.Errorf("file does not exist")
        } else if os.IsPermission(err) {
            return fmt.Errorf("permission denied")
        } else {
            return err
        }
    }
    return nil
}

In the above code example, the foo() function first calls the os.Stat() method to check whether the file exists. If the file does not If it exists, a value of error type will be returned. We can query this error value to determine the real cause of the error and return error information accordingly. This method is more flexible than throwing an exception because it allows the caller to choose whether to handle the error, and it also allows multiple error messages to be returned at the same time.

However, not all errors need to be handled immediately, especially some non-critical errors. In this case, the programmer can decide whether to ignore these errors. By using "_" in the code, the error return value can be ignored. This method is not suitable for all situations, but for errors that do not affect program execution and do not require any information to be logged or fed back, using underscore can make your code more concise and easier to read.

Defer can be used in Go language to catch panic exceptions. The function of defer is to perform some operations when the program exits. These operations will be performed regardless of whether the program exits normally or abnormally. If the built-in panic function is called in the defer function, the program will exit abnormally. Under normal circumstances, it is common practice to use defer and recover to catch and handle exceptions in programs. The recover function is provided in the Go language to capture panic exceptions and restore the state of the program after the program continues execution.

For example, as shown below:

func main() {
    defer func() {
        if r := recover(); r != nil {
            log.Printf("Recovering from panic: %v", r)
        }
    }()
    panic("this is a panic")
}

In the above code, the panic() method is called in the main() function. When the program executes a panic exception, panic() The function will stop the program and print out the error stack information of the exception. However, using the panic function in the defer function can trigger panic again, but this error will be captured by the recover() function in the defer function, and relevant recovery information will be printed out, so that the program can exit normally.

In short, in the Go language, exception handling mechanisms are rarely used, but more emphasis is placed on error handling mechanisms. Handling program errors through function return values ​​can make the program logic clearer and more readable, and provide better error handling and feedback mechanisms. Using defer and recover in a program can not only prevent the program from exiting abnormally by catching exceptions, but also provide a recovery mechanism for the program state. Using these techniques, you can easily handle program exceptions in the Go language.

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