Go语言之init函数

package postgres
import (
 "database/sql"
 "database/sql/driver"
 "errors"
)
// PostgresDriver provides our implementation for the
// sql package.
type PostgresDriver struct{}
// Open provides a connection to the database.
func (dr PostgresDriver) Open(string) (driver.Conn, error) {
 return nil, errors.New("Unimplemented")
}
var d *PostgresDriver
// init is called prior to main.
func init() {
 d = new(PostgresDriver)
 sql.Register("postgres", d)
}

// Sample program to show how to show you how to briefly work
// with the sql package.
package main
import (
 "database/sql"
 _ "github.com/goinaction/code/chapter3/dbdriver/postgres"
)
// main is the entry point for the application.
func main() {
 sql.Open("postgres", "mydb")
}

_ "github.com/goinaction/code/chapter3/dbdriver/postgres"