Can't unlock bootloader Moto G5 XT1672

I'm trying to unlock the bootloader on my Moto G5, the adb commands works, but I can't find my device in the command prompt when it is in fastboot mode. I was following the instructions on this tutorial, but when running the adb device command to get my serial number, the PC can't find the device. I checked the USB cable and the connection between the device and the computer and everything is ok. To enter the fastboot mode I was using the adb reboot bootloadercommand on Windows. Android 8.1.0 Security patch: October 1, 2018