code: func (b *Buffer) consume(n int) ([]byte, bool) {
  	if !b.Has(n) {
  		return nil, false
  	}
  	rval := b.data[:n]
  	b.data = b.data[n:]
  	return rval, true
  }
docs: // consume consumes n bytes from the Buffer. It returns nil, false if there
  // aren't enough bytes left.