1 error[E0373]: closure may outlive the current function, but it borrows `books`, which is owned by the current function
2 --> $DIR/borrowck-escaping-closure-error-1.rs:13:11
4 LL | spawn(|| books.push(4));
5 | ^^ ----- `books` is borrowed here
7 | may outlive borrowed value `books`
9 note: function requires argument type to outlive `'static`
10 --> $DIR/borrowck-escaping-closure-error-1.rs:13:5
12 LL | spawn(|| books.push(4));
13 | ^^^^^^^^^^^^^^^^^^^^^^^
14 help: to force the closure to take ownership of `books` (and any other referenced variables), use the `move` keyword
16 LL | spawn(move || books.push(4));
19 error: aborting due to previous error
21 For more information about this error, try `rustc --explain E0373`.