fix: optimize random value generator

src/models.rs

@@ -185,14 +185,15 @@ impl Token {
     }
 
     pub fn rand(lenth: i32) -> String {
+        use rand::Rng;
         let token_string = TOKEN_SYMBOLS.to_string();
+        let len = TOKEN_SYMBOLS.len();
         let mut ret = String::new();
+        let mut rng = rand::thread_rng();
         for _ in 0..lenth {
-            let index = (rand::random::<i8>() as i8).abs() % 63;
-
-            ret.push(token_string.chars().nth(index as usize).unwrap());
+            let index: usize = rng.gen_range(0, len);
+            ret.push(token_string.chars().nth(index).unwrap());
         }
-
         ret
     }
 }