chore: add comment

Author: ovr

rust/cubesql/pg-srv/src/values/timestamp.rs

@@ -11,6 +11,7 @@ use chrono::{
     prelude::*,
 };
 use chrono_tz::Tz;
+use std::io::Error;
 use std::{
     fmt::{self, Debug, Display, Formatter},
     io,
@@ -122,10 +123,14 @@ impl ToProtocolValue for TimestampValue {
             None => self.to_naive_datetime(),
             Some(_) => self.to_fixed_datetime()?.naive_utc(),
         };
+
         let n = ndt
             .signed_duration_since(pg_base_date_epoch())
             .num_microseconds()
-            .unwrap();
+            .ok_or(Error::new(
+                io::ErrorKind::Other,
+                "Unable to extract number of seconds from timestamp",
+            ))?;
 
         buf.put_i32(8);
         buf.put_i64(n);