What is the reason to have GOPATH set to my workspace?

I read everywhere that my GOPATH must be set to my workspace. If I do that and use go get to get packages from for example GitHub, they are all added to my workspace though, which I don't find particularly useful because it clutters my workspace. In my workspace I expect to find MY code and my code only.

So I now have my own repos in ~/repos/go and left my GOPATH to be the default ~/go. This works perfect. All libraries I import live in ~/go, which keeps my own workplace ~/repos/go nice and clean. This works great for me, so I'm not sure why this is not the recommended way of working.

Am I missing something? Are there things I break or are functionalities not working in this way?

Edit

To explain why my question is different from this question: I know what GOPATH does (define a place to put packages when using go get and a place to import packages from), but I was unaware of why you need to have the public code in the same place as your own code. Turns out there is no need for it, as explained by @peterSO in the (excellent) answer I accepted below.

Solution

go help gopath

Go searches each directory listed in GOPATH to find source code, but new packages are always downloaded into the first directory in the list.

$GOPATH is a directory list. For example, on Linux,

export GOPATH=$HOME/gopublic:$HOME/goprivate

go get places all downloads in the first directory in the list: $HOME/gopublic. Put all your packages in the second directory in the list: $HOME/goprivate.