Appendf returns an error that wraps the given errors.

As finds the first error in err's tree that matches target, and if one is found, sets target to that error value and returns true.

Format wraps err with fmt.Errorf if err is not nil If err is nil returns nil.

Is reports whether any error in err's tree matches target.

Join returns an error that wraps the given errors.

New returns an error that formats as the given text.

Unwrap returns the result of calling the Unwrap method on err, if err's type contains an Unwrap method returning error.

ErrUnsupported indicates that a requested operation cannot be performed, because it is unsupported.