message: Remove clippy warning in mac os
  As pointed out, currently cargo clippy yields warning in mac os machine.
  To resolve it, I made a small module named timeout_test to mark configuration easily -
diff: @@ -408,10 +408,17 @@ async fn sled_transaction_gc() {
  );
  }
  +#[cfg(not(any(target_os = "macos", target_os = "ios")))]
  +mod timeout_tests {
  + use super::*;
  +
  const TX_TIMEOUT: Option<u128> = Some(200);
  const TX_SLEEP_TICK: Duration = Duration::from_millis(201);
  -#[cfg(not(any(target_os = "macos", target_os = "ios")))]
  + fn sleep() {
  + std::thread::sleep(TX_SLEEP_TICK);
  + }
  +
  #[tokio::test]
  async fn sled_transaction_timeout_store() {
  let path = &format!("{}/transaction_timeout_store", PATH_PREFIX);
  @@ -424,10 +431,6 @@ async fn sled_transaction_timeout_store() {
  let mut glue1 = Glue::new(storage1);
  let mut glue2 = Glue::new(storage2);
  - let sleep = || {
  - std::thread::sleep(TX_SLEEP_TICK);
  - };
  -
  exec!(glue1 "BEGIN;");
  // glue1 acquires lock
  @@ -543,7 +546,6 @@ async fn sled_transaction_timeout_store() {
  );
  }
  -#[cfg(not(any(target_os = "macos", target_os = "ios")))]
  #[tokio::test]
  async fn sled_transaction_timeout_alter() {
  let path = &format!("{}/transaction_timeout_alter", PATH_PREFIX);
  @@ -556,10 +558,6 @@ async fn sled_transaction_timeout_alter() {
  let mut glue1 = Glue::new(storage1);
  let mut glue2 = Glue::new(storage2);
  - let sleep = || {
  - std::thread::sleep(TX_SLEEP_TICK);
  - };
  -
  exec!(glue1 "CREATE TABLE TxAlter (id INTEGER, num INTEGER);");
  exec!(glue1 "INSERT INTO TxAlter VALUES (1, 100);");
  @@ -620,10 +618,9 @@ async fn sled_transaction_timeout_alter() {
  test!(glue2 "SELECT * FROM TxSoprano;", Ok(select!(kd | num I64 | I64; 1 100)));
  }
  -#[cfg(not(any(target_os = "macos", target_os = "ios")))]
  #[tokio::test]
  async fn sled_transaction_timeout_index() {
  - use ast::IndexOperator::Eq;
  + use crate::ast::IndexOperator::Eq;
  let path = &format!("{}/transaction_timeout_index", PATH_PREFIX);
  fs::remove_dir_all(path).unwrap_or(());
  @@ -635,10 +632,6 @@ async fn sled_transaction_timeout_index() {
  let mut glue1 = Glue::new(storage1);
  let mut glue2 = Glue::new(storage2);
  - let sleep = || {
  - std::thread::sleep(TX_SLEEP_TICK);
  - };
  -
  exec!(glue1 "CREATE TABLE TxIndex (id INTEGER);");
  exec!(glue1 "INSERT INTO TxIndex VALUES (1);");
  @@ -730,6 +723,7 @@ async fn sled_transaction_timeout_index() {
  Ok(select!(id I64; 1))
  );
  }
  +}
  #[test]
  fn sled_transaction_metadata() {
  