golang雪花算法实现64位的ID的示例代码

package main

import (
    "fmt"
    "sync"
    "time"
)

const (
    // 起始时间戳（2020-01-01）
    twepoch        = 1577836800000
    workerIDBits   = 5
    datacenterIDBits = 5
    sequenceBits   = 12

    maxWorkerID     = -1 ^ (-1 << workerIDBits)
    maxDatacenterID = -1 ^ (-1 << datacenterIDBits)
    maxSequence     = -1 ^ (-1 << sequenceBits)

    workerIDShift      = sequenceBits
    datacenterIDShift  = sequenceBits + workerIDBits
    timestampLeftShift = sequenceBits + workerIDBits + datacenterIDBits
)

type Snowflake struct {
    mu            sync.Mutex
    lastTimestamp int64
    workerID      int64
    datacenterID  int64
    sequence      int64
}

func NewSnowflake(workerID, datacenterID int64) (*Snowflake, error) {
    if workerID < 0 || workerID > maxWorkerID {
        return nil, fmt.Errorf("worker ID must be between 0 and %d", maxWorkerID)
    }
    if datacenterID < 0 || datacenterID > maxDatacenterID {
        return nil, fmt.Errorf("datacenter ID must be between 0 and %d", maxDatacenterID)
    }
    return &Snowflake{
        workerID:      workerID,
        datacenterID:  datacenterID,
        lastTimestamp: -1,
        sequence:      0,
    }, nil
}

func (s *Snowflake) NextID() int64 {
    s.mu.Lock()
    defer s.mu.Unlock()

    timestamp := time.Now().UnixNano() / 1e6
    if timestamp < s.lastTimestamp {
        return 0
    }

    if s.lastTimestamp == timestamp {
        s.sequence = (s.sequence + 1) & maxSequence
        if s.sequence == 0 {
            for timestamp <= s.lastTimestamp {
                timestamp = time.Now().UnixNano() / 1e6
            }
        }
    } else {
        s.sequence = 0
    }

    s.lastTimestamp = timestamp
    return ((timestamp - twepoch) << timestampLeftShift) |
        (s.datacenterID << datacenterIDShift) |
        (s.workerID << workerIDShift) |
        s.sequence
}

func main() {
    sf, err := NewSnowflake(1, 1)
    if err!= nil {
        panic(err)
    }
    id := sf.NextID()
    fmt.Println(id)
}