Use Mitmproxy to Monitor Flow

install mitmproxy on the Mac

brew install mitmproxy

start it

mitmweb --listen-port 9090

connect the iPhone to Mac ( two devices should connect to the same WIFI)

In you Wifi settings, change the Http Proxy part.

install certification on the iPhone

Open http://mitm.it with safari and follow the guide on the images, after download the file, iPhone will tell you to install the certification file manually .

After the installation, you need to enable the certification file in Settings-> General -> About, at the bottom of the page, you will find Certificate Trust Setttings, enable the mitm inside this page.

Done