Why Use Underscores When Importing Packages in Go?

Importing Packages with Side Effects in Go

When examining code that utilizes the go-sqlite3 library, one may encounter an import statement with an underscore preceding it, similar to the following:

import (
        "database/sql"
        "fmt"
        _ "github.com/mattn/go-sqlite3"
        "log"
        "os"
)

This usage of the underscore is a method in Go for importing a package solely for its side effects. As outlined in the Go Specification:

To import a package solely for its side-effects (initialization), use the blank identifier as explicit package name:

import _ "lib/math"

Example: go-sqlite3 Initialization

In the case of go-sqlite3, this underscore import serves the purpose of registering the sqlite3 driver as a database driver through the init() function, without the need to import any other functions from the package:

sql.Register("sqlite3", &SQLiteDriver{})

Once registered, the sqlite3 driver can be employed with the standard library's sql interface, as seen in the following example:

db, err := sql.Open("sqlite3", "./foo.db")

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