Detailed explanation of how to generate random seeds in Go

().UnixNano

This is the most commonly used method, but it is also the method with the greatest safety hazards.

On the surface, the maximum accuracy of the time method is to nanoseconds, but it seems that the absolute nanosecond accuracy cannot be achieved.

The test results were bad and the collision was very high.

import "time"

func TestSeedNanoTime(t *) {
	var seeds = make(map[int64]bool)
	for i := 0; i < 100000; i++ {
		seed := ().UnixNano()
		seeds[seed] = true
		(seed)
	}
	(len(seeds))
}

This method has no collision

import "hash/maphash"

func TestSeedMapHash(t *) {
	var seeds = make(map[int64]bool)
	for i := 0; i < 100000; i++ {
		seed := int64(new().Sum64())
		seeds[seed] = true
		(seed)
	}
	(len(seeds))
}

This method has no collision

import (
	cryptoRand "crypto/rand"
	mathRand "math/rand"
)

func TestSeedCryptoRand(t *) {
	var seeds = make(map[int64]bool)
	for i := 0; i < 100000; i++ {
		var b [8]byte
		_, err := (b[:])
		if err != nil {
			panic("cannot seed math/rand package with cryptographically secure random number generator")
		}
		seed := int64(.Uint64(b[:]))
		seeds[seed] = true
		(seed)
	}
	(len(seeds))
}

Mapping table

This method has no collision

func TestSeedRandomString(t *) {
	const alpha = "abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789"
	size := 8
	var seeds = make(map[int64]bool)
	for i := 0; i < 100000; i++ {
		buf := make([]byte, size)
		for i := 0; i < size; i++ {
			buf[i] = alpha[(len(alpha))]
		}
		seed := int64(.Uint64(buf[:]))
		seeds[seed] = true
		(seed)
	}
	(len(seeds))
}

References

How to properly seed random number generator

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