Designing an API that "stutters" is a very common mistake that many programmers make. reader.Read() is pretty jarring.
There is also nothing wrong with naming variables after what they're for instead of what they are. Consider io.Copy(dst, src). That's nicer than io.Copy(reader1, reader2).
Sure, so call your reader `file` or `network` or `stream`. Don't call it `r`. Nobody is charging you by the character.
It isn't a huge deal when the code is simple, e.g. you create a reader named `r` and in the next line you use it. That's easy to understand. The problem is that the pattern propagates. A few more lines of code are added, the reader is still named `r`. It's name `r` here, so we start putting it in a struct as `r`. Soon enough the codebase is littered with instances of `r`. Not great.
There is also nothing wrong with naming variables after what they're for instead of what they are. Consider io.Copy(dst, src). That's nicer than io.Copy(reader1, reader2).