You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: clock.rs
    path of file: ./repos/phaser/phaser/vendor/tokio/src/time
    
    the code of the file until where you have to start completion: #![cfg_attr(not(feature = "rt"), allow(dead_code))]

//! Source of time abstraction.
//!
//! By default, `std::time::Instant::now()` is used. However, when the
//! `test-util` feature flag is enabled, the values returned for `now()` are
//
    
    pub fn resume() {
        let clock = clock().expect("time cannot be frozen from outside the Tokio runtime");
        let mut inner = clock.inner.lock();

        if inner.unfrozen.is_some() {
            panic!("time is not frozen");
        }

        inner.unfrozen = Some(std::time::Instant::now());
    }