RaspAP 
is a web gui for configuring WiFi on a Raspberry Pi without using the full desktop version. It simplifies WiFi configuration for a Pi running the Lite version of Raspbarian.
You can use RaspAP to be a WiFi client and hot spot at the same time. You can SSH directly in to Pi when there is no other networks available but also connect it to Internet when other WiFi networks are available. YouTube
I have configured one of my Raspberry Pis to be a mobile hotspot by following the instructions on the YouTube site.
I had set up SSH key authentication using ssh-copy-id and while it worked initially, when I tried logging in later I observed what looked like SSH hanging while authenticating. I found [an article](https://www.raedts.biz/tech/ssh-hangs-during-authentication-on-raspberry-pi/) online that described my scenario of SSH hanging during authentication and suggested the issue is due to the use of QoS in Raspbian and SSH access via WiFi. I made the following configuration change on my Raspberry Pis and that fixed the problem. Add IPQoS 0x00 to the end of the following files * /etc/ssh/ssh_config * /etc/ssh/sshd_config