Go: Storing mysql database connection in a global variable ?

Question

I'm using the MySQL driver for Golang provided here https://github.com/go-sql-driver/mysql One of the things I'm trying to do is store the database variable in a global connection. According to the documentation, sql.Open() is supposed to return a pointer to a DB struct, so I tried storing it as var db *DB However, that resulted in the error undefined: DB The next thing I tried was to look at the source code for the MySQL driver, and I found a snippet of code here https://github.com/go-sql-driver/mysql/blob/master/driver.go func (d MySQLDriver) Open(dsn string) (driver.Conn, error) { So, I tried to save the variable as driver.Conn - however, I was unable to (incorrect imports). I wasn't able to import driver either. The last thing I tried was to use reflect to bring the name of the variable to light package main import ( "fmt" "reflect" ) import "database/sql" import _ "github.com/go-sql-driver/mysql" func main() { db, _ := sql.Open("mysql", "root:password@/Tracker") yt := reflect.TypeOf(db).Kind() fmt.Printf("%T: %s
", yt, yt) } Unfortunately, that didn't work either - it shows up as pointer, and not the type of variable it's actually pointing to. I'm at a loss as to how to figure it out now. Thanks in advance for your help!

Chris Gregori · Accepted Answer

You need to qualify the name of the type with the package name: package main import( "database/sql" "github.com/go-sql-driver/mysql" ) var db *sql.DB // Note the sql package provides the namespace func main() { var err error // Make sure not to shadow your global - just assign with = - don't initialise a new variable and assign with := db, err = sql.Open(...) if err != nil { // Handle the error! } } Whether you want to have a global (easy to get started) or pass it around explicitly is up to you, but I'd suggest just keeping it simple for now. If this is going into a web application, you can safely share the *sql.DB connection pool across handlers/requests.

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