Lazy error handling for overly verbose error producers.

errors.go

// accumulates non-nil errors

type errors []error

func (e *errors) Ack(err error) {
	if err != nil {
		*e = append(*e, err)
	}
}

func (e *errors) Err() error {
	if len(*e) == 0 {
		return nil
	}
	return e
}

func (e *errors) Error() string {
	errs := make([]string, len(*e))
	for i, err := range *e {
		errs[i] = err.Error()
	}
	return strings.Join(errs, ",")
}

// use it like this (snippet from a binary decoder)

func readMapStringString(r io.Reader, tgt *map[string]string) error {
	var errs errors
	var mLen int
	errs.Ack(readInt(r, &mLen))
	v := make(map[string]string, mLen)

	var key, val string
	for i := 0; i < mLen; i++ {
		errs.Ack(readString(r, &key))
		errs.Ack(readString(r, &val))
		v[key] = val
	}
	*tgt = v

	return errs.Err()
}