code: func (u *UUID) SetVariant(v byte) {
  	switch v {
  	case VariantNCS:
  		u[8] = (u[8]&(0xff>>1) | (0x00 << 7))
  	case VariantRFC4122:
  		u[8] = (u[8]&(0xff>>2) | (0x02 << 6))
  	case VariantMicrosoft:
  		u[8] = (u[8]&(0xff>>3) | (0x06 << 5))
  	case VariantFuture:
  		fallthrough
  	default:
  		u[8] = (u[8]&(0xff>>3) | (0x07 << 5))
  	}
  }
docs: // SetVariant sets variant bits.