There are multiple reports of problems with the (or any) "upgrade" hanging.
My first question is, did you acquire the latest ISO of Windows 10 to perform the upgrade?
https://www.microsoft.com/en-us/software-download/windows10
Did you mount the ISO, thereby creating a virtual drive, to run Setup.exe from there to perform the in-place upgrade?
Have you reduced your computer configuration to the bare minimum....
Wired USB mouse, wired USB keyboard and monitor?
AND made sure to disconnect any other peripherals, including wireless dongles supporting Bluetooth wireless keyboard / mouse, wireless network adapters and any other sundry USB peripherals.
Do you have any third party security suites installed on your Windows 8.1 machine?