How to implement structured error reporting and error codes in Go?

There are a few different approaches you can take to implement structured error reporting and error codes in Go. Here's one example:

Define error codes as constants: Start by defining error codes as constants using the const keyword. Each error code should have a unique identifier and a descriptive name. For example:

const (
    ErrCodeInvalidInput = "ERR_INVALID_INPUT"
    ErrCodeServerDown   = "ERR_SERVER_DOWN"
    // ...
)

Create a custom error type: Create a custom error type that includes the error message, error code, and any additional information you want to include. You can define a struct that implements the error interface. For example:

type MyError struct {
    message string
    code    string
}

func (e *MyError) Error() string {
    return e.message
}

func NewError(message, code string) error {
    return &MyError{message: message, code: code}
}

Return structured errors: When an error occurs, create an instance of your custom error type using the NewError function and return it. Include the relevant error code as an argument. For example:

func MyFunction() error {
    if err := someOperation(); err != nil {
        return NewError("An error occurred", ErrCodeInvalidInput)
    }
    return nil
}

Check error codes: When you handle errors, you can now check the error code using a type assertion and perform different actions based on the error code. For example:

func HandleError(err error) {
    if myErr, ok := err.(*MyError); ok {
        switch myErr.code {
        case ErrCodeInvalidInput:
            // Handle invalid input error
        case ErrCodeServerDown:
            // Handle server down error
        // ...
        }
    }
    // Handle other types of errors
}

This approach allows you to provide more structured and standardized error reporting, making it easier to handle and understand errors in your code. Note that this is just one example, and you can customize it based on your specific needs.