乌伊德 二进制可排序的通用唯一标识符 16字节长，6字节毫秒时间戳+ 10个随机字节 高效的base-62字符串编码，URL安全 去doc CONSTANTS const StringMaxLen = 22 StringMaxLen is the maximum length of a string representation of a UUID, i.e. as returned by UUID.String() VARIABLES var Max = UUID{