Is it idiomatic having non-interfaces called like "*er"

Question

The "Effective Go" states:

By convention, one-method interfaces are named by the method name plus an -er suffix or similar modification to construct an agent noun: Reader, Writer, Formatter, CloseNotifier etc.

bufio.io package contains this:

// Reader implements buffering for an io.Reader object.
type Reader struct {
    buf          []byte
    rd           io.Reader
    r, w         int
    err          error
    lastByte     int
    lastRuneSize int
}

Is it idiomatic having structs named like "*er"? Especially in this case it's a struct with the same name as io.Reader which is an interface.

Answer 1

If it's not in Effective Go or the specs then it's a matter of opinion really, I'd say it's fine as long as it makes sense.

Using bufio.Reader or bytes.Reader as an example, they make perfect sense to be named that way.