code: func (d *Decoder) skipSpaces() byte {
  loop:
  	if d.pos == d.end {
  		return 0
  	}
  	switch c := d.data[d.pos]; c {
  	case ' ', '\t', '\n', '\r':
  		d.pos++
  		goto loop
  	default:
  		return c
  	}
  }
docs: // returns the next char after white spaces