What Does the Underscore in a Go Import Statement Mean?

Unveiling the Mystery of the Underscore in Import Statements

In the enigmatic world of programming, certain symbols possess hidden powers. One such symbol is the underscore, which frequently graces the prefix of import statements. In this article, we unravel the enigmatic purpose of this mysterious character.

Consider the following code snippet from the popular go-sqlite3 library:

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

What does the underscore preceding the import statement of "github.com/mattn/go-sqlite3" signify?

The underscore in this context serves a specific purpose: importing a package solely for its side effects. The Go Specification provides the following elucidation:

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

In the case of go-sqlite3, the underscore import accomplishes a crucial task. It enables the side-effect of registering the sqlite3 driver as a database driver within the init() function, without importing any additional functions. This registration allows you to seamlessly interact with sqlite3 using the standard library's sql interface:

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

So, the underscore in import statements is a silent guardian, subtly registering packages for their side effects. It may not appear in the foreground, but its impact is undeniable.

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