read expiration from Set command + tests

src/commands/set.rs

@@ -1,6 +1,7 @@
-use std::io::Cursor;
+use std::{io::Cursor, time::Duration};
 
 use bytes::{Buf as _, Bytes};
+use tokio::time::Instant;
 
 use crate::{
     Result,
@@ -41,9 +42,15 @@ impl Set {
 
         let data = bytes.copy_to_bytes(value_length);
 
+        let expiration: Option<Instant> = match bytes.try_get_u8()? {
+            1 => Some(Instant::now() + Duration::from_secs(bytes.try_get_u64()?)),
+            0 => None,
+            _ => return Err(AppError::UnexpectedCommandData),
+        };
+
         Ok(Self {
             key,
-            value: Value::new(data, None),
+            value: Value::new(data, expiration),
         })
     }
 }