How Can Go's Blank Identifier Enable Package Initialization Without Explicit Function Calls?

Using Blank Identifiers for Package Initialization in Go

The Go programming language allows importing packages solely for their side effects through the use of a blank identifier. This technique is particularly useful when invoking the init function of a package without employing its exported functions.

One practical application of this construct is in database drivers. Consider the go-sqlite3 package, which provides a driver for SQLite databases. To initialize the driver, the package defines an init function:

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

By importing the go-sqlite3 package with a blank identifier, an application can utilize the database driver without explicitly calling any of its methods:

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

Another example is illustrated in the article "Understanding Golang Packages." Here, the init method is used to register a new file system type:

import _ "mypkg/fs"

package main

func init() {
    fsys := &FileSystem{}
    // Register the file system type.
}

The blank identifier allows the application to invoke the init function without exposing the fs package's functions:

import _ "mypkg/fs"

package main

// Use the file system type, registered in the init function.

In summary, using blank identifiers for importing packages in Go provides a concise and convenient way to leverage the functionality of a package solely through its init function, without requiring the use of its exported functions.

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