10 Golang Error Handling Best Practices

Error handling is an important part of any programming language. In Golang, there are multiple ways to handle errors. In this article, we will discuss 10 best practices for error handling in Golang.

1. Use errors.New() to create an error

The errors.New() function returns an error that formats as the given text. It’s a standard way of creating an error in Go, and it’s used by the package itself. So, when you see code like this:

if err != nil {
return err
}
It’s generally best to use errors.New() to create the error. That way, if you ever need to change the text of the error, you can do so in one place.

Of course, there are times when you might want to use a different function to create an error. For example, you might want to use fmt.Errorf() if you need to interpolate values into the error message. But in general, errors.New() is the best choice.

2. Wrap the error with fmt.Errorf()

When you wrap the error with fmt.Errorf(), you can add more context to the error message. This is important because it can help you and others debug the issue more easily.

For example, let’s say you have a function that returns an error if the input is invalid. If you simply return the error without wrapping it, the message will be something like “invalid input”. But if you wrap it with fmt.Errorf(), you can add more context, such as “invalid input: %s”, where %s is the actual input.

This may seem like a small change, but it can make a big difference when you’re trying to debug an issue. So always remember to wrap your errors with fmt.Errorf()!

3. Return a nil error if everything is fine

When you return a nil error, it’s an explicit signal to the caller that everything went well and that they can continue with their work. On the other hand, if you return a non-nil error, it’s an explicit signal that something went wrong and that the caller needs to handle the error.

This may seem like a small distinction, but it’s actually a very important one. By returning a nil error when everything is fine, you make it easier for the caller to write correct code. And by returning a non-nil error when something goes wrong, you make it easier for the caller to handle errors correctly.

4. Create custom type for your error

When you create a custom type for your error, you can add methods to it. This gives you more control over how your error is handled. For example, you could add a method that prints the stack trace of the error, or a method that returns the underlying cause of the error.

Creating a custom type also allows you to attach additional information to your error. This can be useful for debugging purposes. For example, you could include the line number where the error occurred, or the file name and path.

Finally, creating a custom type makes it easier to document your code. When you use a custom type, you can add comments to the methods, explaining what they do and how they should be used.

5. Don’t use panic() and recover()

When you use panic(), it stops the ordinary flow of execution and begins unwinding the stack. This process can be very expensive, especially if you’re panicking in a tight loop. In addition, if you use recover() to handle the panic, you may hide important information about the real cause of the problem.

It’s much better to use proper error handling techniques, such as returning errors from functions or using defer to cleanup resources. By doing this, you can avoid the performance overhead of panicking and ensure that your code is more robust.

6. Check the error immediately after function call

When you check the error right away, it’s easier to understand which function caused the problem. If you wait to check the error later on in the code, it might not be clear which function caused the issue.

It’s also important to remember that errors can be chained together. So, if you have a function that calls another function, and that function returns an error, you need to check both errors. By checking the error immediately, you can avoid having to debug your code later on.

7. Handle the error in the same function where it was created

If you don’t handle an error in the same function where it was created, then you have to pass the error up the call stack. This can quickly become unwieldy, and it’s easy to forget to check for errors at each level.

It’s much simpler to just handle the error right where it occurred. This way, you know that the error has been handled and you don’t have to worry about it anymore.

Of course, there are exceptions to this rule. For example, if you’re using a library function that returns an error, you may want to handle the error in the caller so that you can gracefully handle the error and provide a better user experience.

But in general, it’s best to handle errors as close to where they occur as possible.

8. Log the error before returning it

If you return the error without logging it first, there’s a chance that the caller will simply ignore the error. By logging it first, you ensure that the error is recorded, even if the caller doesn’t do anything with it.

This is especially important for errors that might not be immediately apparent. For example, if an API call fails but the caller continues to use the data returned by the API, the failure might not be noticed until much later. By logging the error when it happens, you can more easily track down the cause of the problem.

9. Always return the error as the last parameter

When you return the error as the last parameter, it’s easier to use the function in a defer statement. For example, if you have a function that opens a file and returns an error, you can easily close the file in a defer statement like this:

func main() {
f, err := os.Open(“filename.ext”)
if err != nil {
log.Fatal(err)
}
defer f.Close()

// do something with the open file
}

If the error was returned as the first parameter, you would have to do this:

func main() {
f, err := os.Open(“filename.ext”)
if err != nil {
log.Fatal(err)
}
defer func() {
if err := f.Close(); err != nil {
log.Fatal(err)
}
}()

// do something with the open file
}

As you can see, returning the error as the last parameter is much cleaner and simpler.

10. Use multierror package to aggregate multiple errors

If you have a function that can return multiple errors, it can be tempting to just return the first error that occurs. However, this can lead to lost information because the other errors are not returned.

The multierror package allows you to aggregate multiple errors into a single error. This way, you can still return all the errors and handle them all at once.

One caveat with using the multierror package is that you need to make sure that your errors are actually different types. If they are all of the same type, then they will be aggregated into a single error.

This can be avoided by using different types of errors, or by using the errors.Is() function to check if two errors are of the same type.