code: func (f *field) escape() field {
  	pos := 0
  	for i := 0; i < len(f.str); i++ {
  		c := f.str[i]
  		if i+1 < len(f.str) && f.str[i] == '\\' {
  			c = f.escapeChar(f.str[i+1])
  			i++
  		}
  
  		f.str[pos] = c
  		pos++
  	}
  	return field{f.str[:pos], f.maybeNull, f.enclosed}
  }
docs: // escape handles escape characters when running load data statement.
  // See http://dev.mysql.com/doc/refman/5.7/en/load-data.html
  // TODO: escape only support '\' as the `ESCAPED BY` character, it should support specify characters.