fix(driver): Extract scheme from DSN using sqlcon.GetDriverName

[kaorimatz]

Related issue

#145

Proposed changes

Extract a scheme from a DSN string using sqlcon.GetDriverName instead of url.Parse since a DSN string for MySQL is no longer always parsable with url.Parse after this change (Ref: golang/go#33646).

$ cat <<EOF > main.go
package main

import (
        "fmt"
        "net/url"
)

func main() {
        fmt.Println(url.Parse("mysql://tcp(127.0.0.1:3306)/"))
}
EOF
$ go version
go version go1.14 darwin/amd64
$ go run main.go
<nil> parse "mysql://tcp(127.0.0.1:3306)/": invalid port ":3306)" after host

Checklist

• I have read the contributing guidelines
• I have read the security policy
• I confirm that this pull request does not address a security vulnerability. If this pull request addresses a security
  vulnerability, I confirm that I got green light (please contact [email protected]) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation within the code base (if appropriate)
• I have documented my changes in the developer guide (if appropriate)

Further comments

[aeneasr]

thank you!