Databases

One of the most asked questions I get about web development in Go is how to connect to a SQL database. Thankfully, Go has a fantastic SQL package in the standard library that allows us to use a whole slew of drivers for different SQL databases. In this example we will connect to a SQLite database, but the syntax (minus some small SQL semantics) is the same for a MySQL or PostgreSQL database.

package main

import (
    "database/sql"
    "fmt"
    "log"
    "net/http"

    _ "github.com/mattn/go-sqlite3"
)

func main() {
    db := NewDB()
    log.Println("Listening on :8080")
    http.ListenAndServe(":8080", ShowBooks(db))
}

func ShowBooks(db *sql.DB) http.Handler {
    return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
        var title, author string
        err := db.QueryRow("select title, author from books").Scan(&title, &author)
        if err != nil {
            panic(err)
        }

        fmt.Fprintf(rw, "The first book is '%s' by '%s'", title, author)
    })
}

func NewDB() *sql.DB {
    db, err := sql.Open("sqlite3", "example.sqlite")
    if err != nil {
        panic(err)
    }

    _, err = db.Exec("create table if not exists books(title text, author text)")
    if err != nil {
        panic(err)
    }

    return db
}

Exercises

Make use of the Query function on our sql.DB instance to extract a collection of rows and map them to structs.
Add the ability to insert new records into our database by using an HTML form.
go get github.com/jmoiron/sqlx and observe the improvements made over the existing database/sql package in the standard library.