自己署名証明書を使用すると TLS 接続が失敗するのはなぜですか?それを修正するにはどうすればよいですか?

CA_Pool := x509.NewCertPool()
severCert, err := ioutil.ReadFile("./cert.pem")
CA_Pool.AppendCertsFromPEM(severCert)

config := tls.Config{RootCAs: CA_Pool}

cert, err := tls.LoadX509KeyPair("./cert.pem", "./key.pem")
config := tls.Config{Certificates: []tls.Certificate{cert}}

client: dial: x509: certificate signed by unknown authority 
(possibly because of "x509: invalid signature: parent certificate
cannot sign this kind of certificate" while trying to verify 
candidate authority certificate "serial:0")

certTemplate := &x509.Certificate{
    IsCA: true,
    KeyUsage: x509.KeyUsageCertSign,
    // ... other certificate parameters
}