You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: load.go
    path of file: ./repos/kubelogin/pkg/tlsclientconfig/loader
    
    the code of the file until where you have to start completion: // Package loader provides loading certificates from fil
    
func addFile(p *x509.CertPool, filename string) error {
	b, err := os.ReadFile(filename)
	if err != nil {
		return fmt.Errorf("could not read: %w", err)
	}
	if !p.AppendCertsFromPEM(b) {
		return errors.New("invalid certificate")
	}
	return nil
}