Error handling in Go: How to write good error handling code

No matter which programming language you are in, error handling is an essential part. In the Go language, there is a good error handling mechanism that can help programmers easily deal with errors and exceptions. This article will focus on how to write excellent error handling code to improve code quality and program stability.

1. Basic knowledge of error handling

In the Go language, an error is regarded as an ordinary value, which can be processed and passed. Each function may return a value of error type. If an error occurs, it will return a non-nil error value, otherwise it will return nil.

The error type in the Go language is the built-in interface type error, which has only one method:

type error interface {

Error() string

}

This interface A method Error() is defined, which returns a string indicating error information.

Therefore, we can use if err != nil to determine whether an error occurred. If an error occurs, we can handle it accordingly according to the specific situation. Under normal circumstances, we will use the log package to output log information, return error information to the upper-level caller, or take additional measures to avoid errors from happening again.

2. Best practices for error handling

2.1 Return clear error information

The good error handling mechanism in the Go language can provide users with more information Clear error messages help them quickly find the problem. Therefore, when writing Go programs, it is best to provide clear error information for each error so that users can quickly locate and solve the problem.

For example:

if _, err := os.Open(filePath); err != nil {

return fmt.Errorf("failed to open file %s: %v", filePath, err)

}

In the above code , using fmt.Errorf() to wrap the error message, providing a clear error message: an error occurred when opening the file, including the specific file name and error message.

2.2 When you don’t need a specific error type, use errors.New() to create errors

In the Go language, it is very convenient to use errors.New() to create errors. If we need to return an error that does not contain specific information, we can use errors.New() to create a new error.

For example:

return errors.New("something went wrong")

2.3 Avoid nested errors

When handling errors, you may encounter To the case of nested errors, i.e. one error may lead to a larger error. At this time, we need to handle errors carefully to avoid nested errors.

One way to avoid nested errors is to separate the function where nested errors may occur into another function that handles all errors.

For example:

func doSomething() error {

if _, err := os.Open(filePath); err != nil {
    return fmt.Errorf("failed to open file %s: %v", filePath, err)
}
// do something
return nil

}

func main() {

if err := doSomething(); err != nil {
    log.Fatalf("failed to do something: %v", err)
}

}

In the above code, we decompose the function doSomething() where an error may occur into two functions, which avoids the problem of nested errors and makes the code clearer and easier to understand.

2.4 When errors occur on multiple lines, use semicolons to separate them

In the Go language, errors usually occupy multiple lines. At this time, semicolons should be used to separate errors to make them clear and easy to read.

For example:

if value < minValue || value > maxValue {

return fmt.Errorf(
    "value %d is out of range [%d, %d]; %s",
    value, minValue, maxValue, errAdditionalInfo)

}

In the above code, we use semicolon Multi-line errors are separated to make error messages clearer and easier to read.

3. Panic and recover in Go language

In addition to the above error handling mechanism, Go language also provides panic and recovery mechanisms for handling serious errors and Recovery procedures.

When an unrecoverable error occurs in the program, you can use the panic() function to throw an exception. At this time, the program will immediately stop execution and print out an error message.

For example:

func doSomething() {

if _, err := os.Open(filePath); err != nil {
    panic(fmt.Sprintf("failed to open file %s: %v", filePath, err))
}
// do something

}

In the above code, if an error occurs when opening the file, the program will stop immediately Execute and throw an exception.

On the other hand, the recover() function can resume the execution of the program after a panic occurs in the program. The recover() function can only be used in the defer function, which is used to catch panic and stop the panic from passing to the outer layer.

For example:

func main() {

defer func() {
    if err := recover(); err != nil {
        log.Fatalf("recover from panic: %v", err)
    }
}()
doSomething()

}

In the above code, we use the defer function plus recover() to restore execution of the program. When a program panics, the recover() function will be called in the defer function to capture the panic and print error information.

4. Summary

Excellent error handling is a sign of code quality and can make the code more robust and secure. In the Go language, a good error handling mechanism can easily handle and pass errors, and the panic and recover functions can be used to handle serious errors and resume program execution. In order to write good error handling code, we need to follow best practices and always pay attention to the clarity and clarity of error messages.

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