How does Go handle errors? How is it customary to propagate an error from an external package to a higher level without revealing internal details?

In Go, errors are represented by the error type, which is an interface. It is common to return an error value from a function and check it at the call site.

To propagate an error from an external package without revealing internal details, wrappers and error formatting are used with the fmt or errors packages.

For example, you can add context to an error without exposing its internal structure:

if err := externalPackage.DoSomething(); err != nil {
    return fmt.Errorf("failed to perform operation: %w", err)
}

Here, %w allows wrapping the original error, enabling further checks with errors.Is or errors.As.

Thus, external code receives a clear error message without access to internal implementation details, while still allowing detailed error analysis if needed.