code: func lexMode(v []byte) lexModeValue {
  	var (
  		r      rune
  		w      int
  		offset int
  	)
  
  	for {
  		r, w = utf8.DecodeRune(v[offset:])
  		offset += w
  		if unicode.IsSpace(r) {
  			continue
  		}
  		if r == '{' {
  			return lexModeJson
  		}
  		break
  	}
  
  	return lexModeHcl
  }
docs: // lexMode returns whether we're going to be parsing in JSON
  // mode or HCL mode.