This is a Go implementation of Twitter Snowflake.

The most useful aspect of these IDs is they are roughly sortable and when generated at roughly the same time, should have values in close proximity to each other.

Each id will be a 64-bit number represented, structured as follows:

6  6         5         4         3         2         1
3210987654321098765432109876543210987654321098765432109876543210

ttttttttttttttttttttttttttttttttttttttttttmmmmmmmmmmssssssssssss

where

• s (sequence) is a 12-bit integer that increments if called multiple times for the same millisecond
• m (machine id) is a 10-bit integer representing the server id
• t (time) is a 42-bit integer representing the current timestamp in milliseconds the number of milliseconds to have elapsed since 1491696000000 or 2017-04-09T00:00:00Z

The 64-bit unsigned integer is base-63 encoded using the following URL-safe characters, which are ordered according to their ASCII value.

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz~

A binary sort of a list of encoded values will be correctly ordered according to the numerical representation.