fix(random): prevent UniqueID collisions from per-call time seeding (#1860)

UniqueID (and Random/RandomString/RandomInt via newRand) created a fresh *rand.Rand seeded with time.Now().UnixNano() on every call. When invoked in a tight loop or in parallel on machines with coarse timer resolution (e.g. Windows), consecutive calls observe the same timestamp, get the same seed, produce the same sequence, and return identical 'unique' IDs.

This leads to duplicate resource names / tfstate keys and flaky parallel tests. TestUniqueID reproduces it reliably on Windows.

Use the process-global, auto-seeded (Go 1.20+) and concurrency-safe math/rand source instead. This removes the collision source and also avoids allocating a new generator on every call. No public API changes; output remains non-deterministic as before (the previous code seeded from the wall clock, so it was never deterministic either).

Amp-Thread-ID: https://ampcode.com/threads/T-019f32a2-bbac-752b-bbf2-2ee88229b925

Co-authored-by: zuwasi <zuwasi@users.noreply.github.com>
Co-authored-by: Amp <amp@ampcode.com>

Author: zuwasi

modules/core/random/random.go

@@ -4,12 +4,11 @@ package random
 import (
 	"bytes"
 	"math/rand"
-	"time"
 )
 
 // Random generates a random int between min and max, inclusive.
 func Random(min int, max int) int {
-	return newRand().Intn(max-min+1) + min
+	return rand.Intn(max-min+1) + min
 }
 
 // RandomInt picks a random element in the slice of ints.
@@ -33,15 +32,9 @@ const uniqueIDLength = 6 // Should be good for 62^6 = 56+ billion combinations
 func UniqueID() string {
 	var out bytes.Buffer
 
-	generator := newRand()
 	for i := 0; i < uniqueIDLength; i++ {
-		out.WriteByte(base62chars[generator.Intn(len(base62chars))])
+		out.WriteByte(base62chars[rand.Intn(len(base62chars))])
 	}
 
 	return out.String()
 }
-
-// newRand creates a new random number generator, seeding it with the current system time.
-func newRand() *rand.Rand {
-	return rand.New(rand.NewSource(time.Now().UnixNano()))
-}