I would choose Python for web development, but then I don't know Go. There are Web frameworks for Go as well. However, if you use Python with Django or Flask, you will probably have an easier time hiring developers who are familiar with those frameworks if your app takes off.
I don't think the speed of the language is going to be a limiting factor (in webdev it's usually download size or database queries that slow you down). If it ends up being an issue, there are things like Cython for that.
Python lets you work at a high level of abstraction, letting you get more done faster, which wouldn't usually be the main focus of a systems language like Go, but again I don't know Go, so it could be great at that as well for all I know.
Where I would start looking at Go would be if I wanted a lot of low level control, e.g. of system calls, memory, drivers, threading. I would also look at Rust in this case, as it's another newish systems language that has a great community.
Okay. Thank you
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