seed timeout randomness from crypto/rand to ensure different nodes us…

…e different sequences of random timeouts. Fixes issue #50

util.go

@@ -5,18 +5,29 @@ import (
 	crand "crypto/rand"
 	"encoding/binary"
 	"fmt"
+	"math/big"
 	"math/rand"
 	"time"
 
 	"github.com/hashicorp/go-msgpack/codec"
 )
 
+var rnd = rand.New(rand.NewSource(newSeed()))
+
+func newSeed() int64 {
+	r, err := crand.Int(crand.Reader, big.NewInt(2^63))
+	if err != nil {
+		panic(fmt.Errorf("failed to read random bytes: %v", err))
+	}
+	return r.Int64()
+}
+
 // randomTimeout returns a value that is between the minVal and 2x minVal.
 func randomTimeout(minVal time.Duration) <-chan time.Time {
 	if minVal == 0 {
 		return nil
 	}
-	extra := (time.Duration(rand.Int63()) % minVal)
+	extra := (time.Duration(rnd.Int63()) % minVal)
 	return time.After(minVal + extra)
 }