Multi-Error Aggregation and Hierarchical Type Matching with Slice Unwrapping

package main
 
import (
	"errors"
	"fmt"
	"strings"
)
 
type MultiError struct {
	Errors []error
}
 
func (m *MultiError) Error() string {
	var msgs []string
	for _, err := range m.Errors {
		msgs = append(msgs, err.Error())
	}
	return fmt.Sprintf("%d errors occurred: %s", len(m.Errors), strings.Join(msgs, "; "))
}
 
func (m *MultiError) Unwrap() []error {
	return m.Errors
}
 
type NetworkTimeoutError struct {
	Addr string
}
 
func (e *NetworkTimeoutError) Error() string {
	return fmt.Sprintf("timeout accessing %s", e.Addr)
}
 
func Process(err error) bool {
	var target *NetworkTimeoutError
	return errors.As(err, &target)
}