Go で GoDaddy の SSL 証明書で「不完全な証明書チェーン」エラーが発生するのはなぜですか?

err := srv.ListenAndServeTLS("cert/myalcoholist.pem","cert/myalcoholist.key")

cert, err := tls.LoadX509KeyPair("cert/myalcoholist.pem","cert/myalcoholist.key")
if err != nil {
    log.Fatalf("server: loadkeys: %s", err)
}
pem, err := ioutil.ReadFile("cert/cert/sf_bundle-g2-g1.crt")
if err != nil {
    log.Fatalf("Failed to read client certificate authority: %v", err)
}
if !certpool.AppendCertsFromPEM(pem) {
    log.Fatalf("Can't parse client certificate authority")
}
tlsConfig := &tls.Config{
    ClientCAs:    certpool,
    Certificates: []tls.Certificate{cert},
}
srv := &http.Server{
    Addr: "myalcoholist.com:443",
    Handler: n,
    ReadTimeout: time.Duration(5) * time.Second,
    WriteTimeout: time.Duration(5) * time.Second,
    TLSConfig: tlsConfig,
}
err := srv.ListenAndServeTLS("cert/myalcoholist.pem","cert/myalcoholist.key")