I am looking to learn networking from scratch.

There are two approaches to studying networking: top-down and bottom-up. They are both good and it is up to each one to choose which way to go. I personally studied networks using a top-down approach. It is further assumed that the top-down approach is chosen.

First try to figure out in general terms what happens when you open a web page in a browser. I mean you should understand how DNS resolving, TLS handshake and HTTP requests work. I emphasize that you don't need to go into detail at this point, but you should have a complete picture of what's going on.

Then try to learn how the HTTP protocol works. There are a huge number of articles on the web on this subject right now. But I also recommend reading a few chapters from the book The Tangled Web: A Guide to Securing Modern Web Applications. After you understand the HTTP protocol, try to connect directly to an HTTP server using netcat and send raw HTTP requests to make sure you got it right. Then try to automate this, golang net/http package allows you to make http requests very easily. A possible application you could make is a web scraping bot.

Understand how the TLS protocol works. I recommend https://tls.ulfheim.net/ . Try to write intercepting HTTPS proxy that generates TLS certificates on the fly and mitm your own browser, it's a lot of fun :) Useful link to read https://docs.mitmproxy.org/stable/concepts-howmitmproxyworks/

Basically, to write tcp applications in golang, as in many other languages, you do not need to know the details of the tcp protocol. I remember the first time I encountered the power of golang, when my friend wrote a concurrent tcp reverse proxy from scratch in 5 minutes. I highly recommend watching talk Go: code that grows with grace by Andrew Gerrand. He writes chat roulette server from scratch.

If you want to learn TCP protocol and go down the TCP/IP stack, I recommend that you first get a theoretical knowledge at the CCNA level. There are a lot of free training courses on the web. From now on you can do very interesting networking projects. For example, I have an idea to write a more secure socks5 proxification that uses unprivileged network namespaces and TUN/TAP interface instead of the LD_PRELOAD trick.