code: func parseFieldLine(l string) (field, rest string, ok bool) {
  	if m := fieldRe.FindStringSubmatch(l); m != nil {
  		return m[1], m[2], true
  	}
  	return
  }
docs: // parseFieldLine recognized strings like "field<space>*:<space>*...".
  //
  // Returns the extracted field name and what is left of the line.
  //
  // No spaces are allowed in the field name part.