func CutBytes(s, sep []byte) (before, after []byte, found bool)
CutBytes slices s around the first instance of sep,
returning the text before and after sep.
The found result reports whether sep appears in s.
If sep does not appear in s, cut returns s, nil, false.
CutBytes returns slices of the original slice s, not copies.
func CutString(s, sep string) (before, after string, found bool)
CutString slices s around the first instance of sep,
returning the text before and after sep.
The found result reports whether sep appears in s.
If sep does not appear in s, cut returns s, "", false.