func colorString(code int, str string) string {
	return fmt.Sprintf("\x1b[%d;1m%s\x1b[39;22m", code, str)
}
colorString convert a string to a color string with color code.
package logging
import (
	"fmt"
	"io"
)
type ColorType uint16
const (
	ColorRed     ColorType = 31
	ColorGreen   ColorType = 32
	ColorYellow  ColorType = 33
	ColorBlue    ColorType = 34
	ColorMagenta ColorType = 35
	ColorCyan    ColorType = 36
	ColorWhite   ColorType = 37
	ColorGray    ColorType = 90
)