Add cache ttl

selector/cache/options.go

@@ -0,0 +1,20 @@
+package cache
+
+import (
+	"time"
+
+	"github.com/micro/go-micro/selector"
+	"golang.org/x/net/context"
+)
+
+type ttlKey struct{}
+
+// Set the cache ttl
+func TTL(t time.Duration) selector.Option {
+	return func(o *selector.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, ttlKey{}, t)
+	}
+}