What does an underscore in front of an import statement mean?

Question

I saw this example from sqlite3 on GitHub :

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


        

Answer 1

Short answer:

It's for importing a package solely for its side-effects.

From the Go Specification:

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

import _ "lib/math"

In sqlite3

In the case of go-sqlite3, the underscore import is used for the side-effect of registering the sqlite3 driver as a database driver in the init() function, without importing any other functions:

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

Once it's registered in this way, sqlite3 can be used with the standard library's sql interface in your code like in the example:

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