When Should You Use Go's Blank Identifier Import?

Importing with Blank Identifier: A Practical Use Case

The Go programming language allows packages to be imported solely for their initialization side effects. This can be achieved by using the blank identifier as the explicit package name, as seen in this example:

import _ "foo/bar"

This import statement suggests that the package foo/bar will be imported for its initialization functions, but its exported functions will not be used in the importing program.

Real-Life Example: Database Driver Registration

One practical use case for this construct lies in database driver registration. A database driver package often contains an initialization function that registers the driver with the database library.

For example, in the go-sqlite3 package, the following init function registers the SQLite3 driver:

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

By importing go-sqlite3 with a blank identifier, the importing program can register the SQLite3 driver without directly using any of its exported functions:

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

func main() {
    // Connect to a SQLite3 database using the registered driver.
}

Other Examples of Initialization Side Effects

Initialization functions can also be used to:

• Set global state: For example, a package might define an initialization function that sets the default logging level.
• Load resources: A package might import a file containing a pre-computed data structure or configuration values into memory.
• Perform cleanup actions: A package might define an initialization function that runs when the package is imported, e.g., to register a resource cleanup callback.

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