Seed math/rand more efficiently

cmd/bb/main.go

@@ -15,6 +15,7 @@ import (
 	"syscall"
 
 	"git.kill0.net/chill9/beepboop/command"
+	"git.kill0.net/chill9/beepboop/lib"
 
 	"github.com/bwmarrin/discordgo"
 	log "github.com/sirupsen/logrus"
@@ -60,7 +61,7 @@ func main() {
 		log.SetLevel(log.DebugLevel)
 	}
 
-	seedRand()
+	lib.SeedMathRand()
 
 	viper.SetDefault("handler.reaction.emojis", defaultReactions)
 	viper.SetEnvPrefix("BEEPBOOP")
@@ -178,16 +179,3 @@ func contains[T comparable](s []T, v T) bool {
 	}
 	return false
 }
-
-func seedRand() {
-	var b [8]byte
-
-	_, err := crypto_rand.Read(b[:])
-	if err != nil {
-		log.Panicf("cannot seed math/rand: %s", err)
-	}
-
-	log.Debugf("seeding math/rand %+v %+v", b, binary.LittleEndian.Uint64(b[:]))
-
-	math_rand.Seed(int64(binary.LittleEndian.Uint64(b[:])))
-}

lib/rand.go

@@ -0,0 +1,34 @@
+package lib
+
+import (
+	crand "crypto/rand"
+	"math"
+	"math/big"
+	"math/rand"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+)
+
+var (
+	once sync.Once
+)
+
+// SeedMathRand Credit: https://github.com/hashicorp/consul/blob/main/lib/rand.go
+func SeedMathRand() {
+	var (
+		n   *big.Int
+		err error
+	)
+
+	once.Do(func() {
+		n, err = crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
+		if err != nil {
+			log.Errorf("cannot seed math/rand: %s", err)
+		}
+
+		log.Debugf("seeding math/rand %+v", n.Int64())
+
+		rand.Seed(n.Int64())
+	})
+}