Connecting to an SQL database

The first thing we need do before connecting to an SQL-like database is identify the particular database that we will be interacting with and import a corresponding driver. In the following examples, we will be connecting to a Postgres database and will utilize the github.com/lib/pq database driver for database/sql. This driver can be loaded via an empty import (with a corresponding comment):

import (
    "database/sql"
    "fmt"
    "log"
    "os"

    // pq is the library that allows us to connect
    // to postgres with databases/sql.
    _ "github.com/lib/pq"
)

Now let's assume that you have exported the Postgres connection string to an environmental variable PGURL. We can easily create an sql.DB value for our connection via the follow code:

// Get the postgres connection URL. I have it stored in
// an environmental variable.
pgURL := os.Getenv("PGURL")
if pgURL == "" {
    log.Fatal("PGURL empty")
}

// Open a database value. Specify the postgres driver
// for databases/sql.
db, err := sql.Open("postgres", pgURL)
if err != nil {
    log.Fatal(err)
}
defer db.Close()

Note that we need to defer the close method on this value. Also, note that creating this value does not mean that you have made a successful connection to the database. This is merely a value used by database/sql to connect to the database when triggered to do so by certain operations (such as a query).

To ensure that we can make a successful connection to the database, we can use the Ping method:

if err := db.Ping(); err != nil {
    log.Fatal(err)
}