fix pool

Author: bbengfort

entropy.go

@@ -17,12 +17,14 @@ import (
 //===========================================================================
 
 var defaultEntropy = func() io.Reader {
-	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
-	return &LockedMonotonicReader{MonotonicReader: Monotonic(rng, 0)}
+	return Pool(func() io.Reader {
+		return Monotonic(rand.New(rand.NewSource(time.Now().UnixNano())), 0)
+	})
 }()
 
 // DefaultEntropy returns a thread-safe per process monotonically increasing
-// entropy source.
+// entropy source. It uses a sync.Pool rather than a sync.Mutex to provide
+// minimal contention for concurrent access.
 func DefaultEntropy() io.Reader {
 	return defaultEntropy
 }
@@ -31,9 +33,7 @@ func DefaultEntropy() io.Reader {
 // Secure Entropy
 //===========================================================================
 
-var secureEntropy = func() io.Reader {
-	return Pool(func() io.Reader { return crand.Reader })
-}()
+var secureEntropy = crand.Reader
 
 // SecureEntropy returns a thread-safe per process monotonically increasing
 // entropy source that uses cryptographically random generation and a sync.Pool

ulid.go

@@ -110,7 +110,7 @@ func MustNewSecure(t time.Time) ULID {
 
 // Make returns a ULID with the current time in Unix milliseconds and
 // monotonically increasing entropy for the same millisecond.
-// It is safe for concurrent use, using a sync.Mutex to protect entropy access.
+// It is safe for concurrent use, using a sync.Pool to minimize contention.
 func Make() (id ULID) {
 	// NOTE: MustNew can't panic since DefaultEntropy never returns an error.
 	return MustNew(Now(), defaultEntropy)

ulid_test.go

@@ -368,6 +368,8 @@ func TestParseRobustness(t *testing.T) {
 }
 
 func TestParseTypes(t *testing.T) {
+	t.Parallel()
+
 	example := ulid.Make()
 	testCases := []struct {
 		input    any