Use bytes.IndexByte instead of bytes.Index for single byte lookup

[moredure]

No description provided.

[erikdubbelboer]

Thanks. I would expect the result to be the same as bytes.Index just calls bytes.IndexByte and the input is a constant. But it seems that as the compiler isn't smart enough to see that strAt never gets modified it isn't able to inline this. Even writing it as bytes.Index(host, []byte("@")) it isn't smart enough.