fix cluster slots algo slightly, thanks to @nickynick for the fix

cluster_crc16.go

@@ -1,6 +1,8 @@
 package radix
 
-import "bytes"
+import (
+	"bytes"
+)
 
 var tab = [256]uint16{
 	0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
@@ -54,8 +56,8 @@ func CRC16(buf []byte) uint16 {
 // taking into account key hash tags
 func ClusterSlot(key []byte) uint16 {
 	if start := bytes.Index(key, []byte("{")); start >= 0 {
-		if end := bytes.Index(key[start+2:], []byte("}")); end >= 0 {
-			key = key[start+1 : start+2+end]
+		if end := bytes.Index(key[start+1:], []byte("}")); end > 0 {
+			key = key[start+1 : start+1+end]
 		}
 	}
 	return CRC16(key) % numSlots

cluster_crc16_test.go

@@ -15,9 +15,21 @@ func TestClusterSlot(t *T) {
 	k := []byte(randStr())
 	crcSlot := ClusterSlot(k)
 
+	// ClusterSlot without handling curly braces
+	rawClusterSlot := func(s string) uint16 {
+		return CRC16([]byte(s)) % numSlots
+	}
+
+	clusterSlotf := func(s string, args ...interface{}) uint16 {
+		return ClusterSlot([]byte(fmt.Sprintf(s, args...)))
+	}
+
 	kk := randStr()
-	assert.Equal(t, crcSlot, ClusterSlot([]byte(fmt.Sprintf("{%s}%s", k, kk))))
-	assert.Equal(t, crcSlot, ClusterSlot([]byte(fmt.Sprintf("{%s}}%s", k, kk))))
-	assert.Equal(t, crcSlot, ClusterSlot([]byte(fmt.Sprintf("%s{%s}", kk, k))))
-	assert.Equal(t, crcSlot, ClusterSlot([]byte(fmt.Sprintf("%s{%s}}%s", kk, k, kk))))
+	assert.Equal(t, crcSlot, clusterSlotf("{%s}%s", k, kk))
+	assert.Equal(t, crcSlot, clusterSlotf("{%s}}%s", k, kk))
+	assert.Equal(t, crcSlot, clusterSlotf("%s{%s}", kk, k))
+	assert.Equal(t, crcSlot, clusterSlotf("%s{%s}}%s", kk, k, kk))
+	assert.Equal(t, rawClusterSlot(string(k)+"{"), clusterSlotf("%s{", k))
+	// if the braces are empty it should match the whole string
+	assert.Equal(t, rawClusterSlot("foo{}{bar}"), ClusterSlot([]byte(`foo{}{bar}`)))
 }