error: calling `&mut Mutex::lock` unnecessarily locks an exclusive (mutable) reference
  --> $DIR/mut_mutex_lock.rs:11:33
   |
LL |     let mut value = value_mutex.lock().unwrap();
   |                                 ^^^^ help: change this to: `get_mut`
   |
   = note: `-D clippy::mut-mutex-lock` implied by `-D warnings`

error: aborting due to previous error