go/src/errors/join.go

// Join returns an error that wraps the given errors.
// Any nil error values are discarded.
// Join returns nil if every value in errs is nil.
// The error formats as the concatenation of the strings obtained
// by calling the Error method of each element of errs, with a newline
// between each string.
//
// A non-nil error returned by Join implements the Unwrap() []error method.
func Join(errs ...error) error { … }

type joinError …

func (e *joinError) Error() string { … }

func (e *joinError) Unwrap() []error { … }