add support for querying entry expiration.

datastore.go

@@ -138,6 +138,7 @@ type TTLDatastore interface {
 
 	PutWithTTL(key Key, value []byte, ttl time.Duration) error
 	SetTTL(key Key, ttl time.Duration) error
+	GetExpiration(key Key) (time.Time, error)
 }
 
 // Txn extends the Datastore type. Txns allow users to batch queries and

query/query.go

 package query
 
 import (
+	"time"
+
 	goprocess "github.com/jbenet/goprocess"
 )
 
@@ -62,12 +64,14 @@ type Query struct {
 	Limit             int      // maximum number of results
 	Offset            int      // skip given number of results
 	KeysOnly          bool     // return only keys.
+	ReturnExpirations bool     // return expirations (see TTLDatastore)
 }
 
 // Entry is a query result entry.
 type Entry struct {
 	Key        string    // cant be ds.Key because circular imports ...!!!
 	Value      []byte    // Will be nil if KeysOnly has been passed.
+	Expiration time.Time // Entry expiration timestamp if requested and supported (see TTLDatastore).
 }
 
 // Result is a special entry that includes an error, so that the client