Reduce dependency chain

internal/rand/rand.go

@@ -0,0 +1,45 @@
+package rand
+
+import (
+	"math/rand"
+	"sync"
+)
+
+// Int returns a non-negative pseudo-random int.
+func Int() int { return pseudo.Int() }
+
+// Intn returns, as an int, a non-negative pseudo-random number in [0,n).
+// It panics if n <= 0.
+func Intn(n int) int { return pseudo.Intn(n) }
+
+// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n).
+// It panics if n <= 0.
+func Int63n(n int64) int64 { return pseudo.Int63n(n) }
+
+// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n).
+func Perm(n int) []int { return pseudo.Perm(n) }
+
+// Seed uses the provided seed value to initialize the default Source to a
+// deterministic state. If Seed is not called, the generator behaves as if
+// seeded by Seed(1).
+func Seed(n int64) { pseudo.Seed(n) }
+
+var pseudo = rand.New(&source{src: rand.NewSource(1)})
+
+type source struct {
+	src rand.Source
+	mu  sync.Mutex
+}
+
+func (s *source) Int63() int64 {
+	s.mu.Lock()
+	n := s.src.Int63()
+	s.mu.Unlock()
+	return n
+}
+
+func (s *source) Seed(seed int64) {
+	s.mu.Lock()
+	s.src.Seed(seed)
+	s.mu.Unlock()
+}