prevent deserializer from tripping up on positive integers

src/state.rs

@@ -29,12 +29,16 @@ pub(crate) mod timestamp {
         type Value = i64;
 
         fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
-            write!(formatter, "a signed integer")
+            write!(formatter, "an integer")
         }
 
         fn visit_i64<E>(self, v: i64) -> Result<Self::Value, E> {
             Ok(v)
         }
+
+        fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E> {
+            Ok(v as i64)
+        }
     }
 
     pub(crate) fn deserialize<'de, D: Deserializer<'de>>(