Error handling with the error interface

Go's multivalue return simplifies returning detailed error descriptions alongside normal values, a practice considered good style. Errors conventionally implement the built-in error interface, defined by an Error() string method. Library writers may implement richer models, such as os.PathError, which records the operation, file path, and underlying system error. Its Error method generates informative strings like "open /etc/passwx: no such file or directory", including context useful even when printed far from the call site. Error strings should ideally identify their origin via prefixes naming the operation or package, as seen in "image: unknown format". Callers requiring precise details can use type switches or assertions to inspect specific errors. For instance, one might check if an error is a *os.PathError and examine its internal Err field to handle recoverable failures, such as running out of disk space, by taking corrective action like deleting temporary files. Scope: Go. Reviewed October 4, 2026.