failed to connect to the database: default addr for network unknown - MySql and Golang

Hey everyone,

I’m currently setting up a mysql database on DigitalOcean and hit the following error when connecting:

failed to connect to the database: default addr for "DATABASE_CONN_STR" network unknown 

Luckily this turned out to be a pretty easy fix. In the mysql driver repo you can see that the only scenario where this error is shown is when the network doesn’t match “tcp” or “unix”.

// Set default network if empty
	if cfg.Net == "" {
		cfg.Net = "tcp"
	}

	// Set default address if empty
	if cfg.Addr == "" {
		switch cfg.Net {
		case "tcp":
			cfg.Addr = "127.0.0.1:3306"
		case "unix":
			cfg.Addr = "/tmp/mysql.sock"
		default:
			return errors.New("default addr for network '" + cfg.Net + "' unknown")
		}

	} else if cfg.Net == "tcp" {
		cfg.Addr = ensureHavePort(cfg.Addr)
	}

To fix it, all that was required was to wrap part of the connection string in tcp or unix.

root:[email protected]:1234/db_name?ssl-mode=required&timeout=10s
root:password@tcp(db-mysite.com:1234)/db_name?ssl-mode=required&timeout=10s

Note that the host name and port on the second line is now wrapped in “tcp(…)”. In my case I didn’t have either set so I find it a bit strange that the “set default address if empty” check was triggered.

Thanks to this stackoverflow post and github link for the info:

• https://github.com/go-sql-driver/mysql/blob/749ddf1598b47e3cd909414bda735fe790ef3d30/dsn.go#L86-L94
• https://stackoverflow.com/a/52808701/522859