出现错误“证书对ServerCommonName有效，对ClientCommonName有效”

I am trying to do a TLS authentication of a remote server. This server is configured with two certificates (one root and one it's own). Locally, I have the same root certificate. I am doing a TLS handshake (to validate that server can be trusted) by creating a client locally. However, on doing that, I am getting error: x509: Certificate is valid for ServerCommonName, not ClientCommonName. When I am trying to validate certificates present by server, ideally, the certificate chain of server should have a root cert that I trust and this is fine. Not able to understand why getting this particular error.

Can someone help? Below is the code...

func CheckTLSendpoint() error {
    getDecoded()
    var tlsConfig tls.Config
    cer, _ := tls.X509KeyPair(ClientCertPem, ClientKeyPem)

    // Checking verification of server certificate by the client is required or not
    rootCA := x509.NewCertPool()
    rootCA.AppendCertsFromPEM(RootCaPEM)

    tlsConfig = tls.Config{
        RootCAs:            rootCA,
        Certificates:       []tls.Certificate{cer},
        ServerName:         "ClientCommonName", //this is common name of my client certificate
    }
    tlsConfig.BuildNameToCertificate()

    rAddr := "10.20.30.40:3325"

    conn, err := net.DialTimeout("tcp", rAddr, 10*time.Second)
    defer conn.Close()

    if err != nil {
        return fmt.Errorf("TCP connection error : %s", err.Error())
    }

    c := tls.Client(conn, &tlsConfig)
    defer c.Close()

    err = c.Handshake()
    if err != nil {
        return fmt.Errorf("TLS connection error :  %s", err.Error())
    }

    return nil
}