VIN of the LoLin-Module is isolated from USB power which makes sense if you use seperate power supplies. But sometimes you want to use the USB-Socket to supply the rest of your circuit.
In that case you need to bridge the diode. You can do so via a simple wire connecting the right leg of the voltage regulator and the VIN-pin:
Warning: There’s the danger of exceeding the maximum current of your USB port, so be careful!