Golang buffer with concurrent readers

I want to build a buffer in Go that supports multiple concurrent readers and one writer. Whatever is written to the buffer should be read by all readers. New readers are allowed to drop in at any time, which means already written data must be able to be played back for late readers.

The buffer should satisfy the following interface:

type MyBuffer interface {
    Write(p []byte) (n int, err error)
    NextReader() io.Reader
}

Do you have any suggestions for such an implementation preferably using built in types?