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")