question

@the_a_man Thanks for working through this with me. Here is the bare-bones minimum sample code that will let you connect to your DataStax Astra database:

package main

import (
    "fmt"
    "crypto/tls"
    "crypto/x509"
    "io/ioutil"
    "path/filepath"
    "github.com/gocql/gocql"
)

func main() {
    var _cqlshrc_host = "31fecf38-2491-4d43-b6ce-22562679f1b8-us-east1.db.astra.datastax.com"
    var _cqlshrc_port = "34567"
    var _username = "erickramirez"
    var _password = "SomeComp7exP4ssword"
    var _query = "SELECT rank, city, country FROM community.cities_by_rank WHERE rank IN ( 1, 2, 3, 4, 5 )"

    cluster := gocql.NewCluster(_cqlshrc_host)
    cluster.Authenticator = gocql.PasswordAuthenticator{
        Username:       _username,
        Password:       _password,
    }
    cluster.Hosts = []string{_cqlshrc_host + ":" + _cqlshrc_port }

    certPath, _ := filepath.Abs("/home/erick/astra-bundle/cert")
    keyPath, _ := filepath.Abs("/home/erick/astra-bundle/key")
    caPath, _ := filepath.Abs("/home/erick/astra-bundle/ca.crt")
    cert, _ := tls.LoadX509KeyPair(certPath, keyPath)
    caCert, _  := ioutil.ReadFile(caPath)
    caCertPool := x509.NewCertPool()
    caCertPool.AppendCertsFromPEM(caCert)
    tlsConfig := &tls.Config{
        Certificates: []tls.Certificate{cert},
        RootCAs:      caCertPool,
    }
    cluster.SslOpts = &gocql.SslOptions{
        Config: tlsConfig,
        EnableHostVerification: false,
    }

    session, _ := cluster.CreateSession()
    var _rank int
    var _city string
    var _country string

    fmt.Println("According to independent.co.uk, the top 5 most liveable cities in 2019 were:")
    iter := session.Query(_query).Iter()
    for iter.Scan(&_rank, &_city, &_country) {
        fmt.Printf("\tRank %d: %s, %s\n", _rank, _city, _country)
    }
}

Sample output

According to independent.co.uk, the top 5 most liveable cities in 2019 were:
    Rank 1: Vienna, Austria
    Rank 2: Melbourne, Australia
    Rank 3: Sydney, Australia
    Rank 4: Osaka, Japan
    Rank 5: Calgary, Canada

Things to note

I've deliberately not coded any error-handling as I wanted to provide a minimum viable sample. I've also intentionally not placed any in-line comments but tried to be as descriptive as possible with the variable names for brevity.

For developers wanting to re-use the code above, you will need to download the secure-connect zipped bundle for your Astra database.

Unzip your copy of secure-connect-your_astra_db.zip which will contain the following files:

ca.crt
cert
cert.pfx
config.json
cqlshrc
identity.jks
key
trustStore.jks

You will need these files to configure the SSL/TLS options. The cqlshrc file contains the connection details for _cqlshrc_host and _cqlshrc_port in the code above. For example:

[connection]
hostname = 31fecf38-2491-4d43-b6ce-22562679f1b8-us-east1.db.astra.datastax.com
port = 34567
ssl = true

Sample data

Here is the test schema I used:

CREATE KEYSPACE community WITH replication = {'class': 'NetworkTopologyStrategy', 'caas-dc': '1'};

CREATE TABLE community.cities_by_rank (
    rank int PRIMARY KEY,
    city text,
    country text
)

The table contents:

 rank | city       | country
------+------------+-----------
    5 |    Calgary |    Canada
   10 |   Adelaide | Australia
    1 |     Vienna |   Austria
    8 |      Tokyo |     Japan
    2 |  Melbourne | Australia
    4 |      Osaka |     Japan
    7 |    Toronto |    Canada
    6 |  Vancouver |    Canada
    9 | Copenhagen |   Denmark
    3 |     Sydney | Australia

Source: "This is the world's most liveable city", independent.co.uk, published 4 September 2019, retrieved 2 May 2020.

Github

I've published the full code and sample data for easier download -- https://github.com/flightc/astra_gocql_connect.

Credits

Huge thanks to Doug Wettlaufer at DataStax Cloud Engineering for his help with the solution. Cheers!