How to use the go-mysql-driver with ssl on aws with a mysql rds instance

I have a RDS instance running on AWS and I want to know how to connect to that instance over ssl.

From this link Using SSL with mysql database. AWS sets up our database registered with a certificate and provides the root certificate for download.
AWS rds root ca

Now the go-mysql-driver provides this information in there documentation to setup an ssl connection.

rootCertPool := x509.NewCertPool()
pem, err := ioutil.ReadFile("/path/ca-cert.pem")
if err != nil {
   log.Fatal(err)
}
if ok := rootCertPool.AppendCertsFromPEM(pem); !ok {
   log.Fatal("Failed to append PEM.")
}
clientCert := make([]tls.Certificate, 0, 1)
certs, err := tls.LoadX509KeyPair("/path/client-cert.pem", "/path/client-    key.pem")
if err != nil {
   log.Fatal(err)
}
clientCert = append(clientCert, certs)
mysql.RegisterTLSConfig("custom", &tls.Config{
                         RootCAs: rootCertPool,
                         Certificates: clientCert,
                        })
db, err := sql.Open("mysql", "user@tcp(localhost:3306)/test?tls=custom")

The example indicates that I need a client certificate and client key.

But amazon only provides the root certificate. How can I use that with go-mysql-driver to connect to my mysql instance?

I'd add a comment to the previous answer, but my reputation isn't high enough. This is working for me:

    rootCertPool := x509.NewCertPool()
    pem, err := ioutil.ReadFile("/path/ca-cert.pem")
    if err != nil {
       log.Fatal(err)
    }
    if ok := rootCertPool.AppendCertsFromPEM(pem); !ok {
       log.Fatal("Failed to append PEM.")
    }
    mysql.RegisterTLSConfig("custom", &tls.Config{
                             ServerName: "qcaurora.cb556lynvxio.us-east-1.rds.amazonaws.com",
                             RootCAs: rootCertPool,
                            })
    db, err := sql.Open("mysql", "user:pass@tcp(qcrds.example.com:3306)/databasename?tls=custom")

The only change from the above is the addition of the ServerName field. I've also clarified the address field for use with a CNAME dns entry and using a password. If you don't use a CNAME to RDS, you could leave out the ServerName field.

I'm using go 1.11 with go-sql-driver/mysql version v1.4.1.

From looking at the docs here and here and here, it looks like you simply need to set the RootCAs value to the root certificate you obtained from AWS. You don't need to set the Certificates value since you aren't using a client cert. So the code would look something like:

rootCertPool := x509.NewCertPool()
pem, err := ioutil.ReadFile("/path/ca-cert.pem")
if err != nil {
   log.Fatal(err)
}
if ok := rootCertPool.AppendCertsFromPEM(pem); !ok {
   log.Fatal("Failed to append PEM.")
}
mysql.RegisterTLSConfig("custom", &tls.Config{
                         RootCAs: rootCertPool,
                        })
db, err := sql.Open("mysql", "user@tcp(localhost:3306)/test?tls=custom")