Update to run tests concurrently

[dinever]

Hi @nak3, thanks for the contrib. This is exactly what we need.

Just one more thing, what do we think about using os.TempDir and filepath.Join to make it platform-independent?

For example:

import (
    "os"
    "fmt"
    "time"
    "path/filepath"
)

testDB := fmt.Sprintf(filepath.Join(os.TempDir(), "ding-testdb-%s"), fmt.Sprintf(time.Now().Format("20060102T150405.000")))

[nak3]

@dinever That's smarter. Thank you for your advice! I updated.

[dinever]

Thanks @nak3!