Fix env_config_* macro doc tests
@@ -142,6 +142,7 @@ macro_rules! env_config {
///
/// Example usage:
/// ```
+/// use std::time::Duration;
/// habitat_core::env_config_duration!(PersistLoopPeriod,
/// HAB_PERSIST_LOOP_PERIOD_SECS,
/// Duration::from_secs(30));
@@ -166,6 +167,7 @@ macro_rules! env_config_duration {
///
/// Example usage:
/// ```
+/// use std::time::Duration;
/// habitat_core::env_config_duration!(ThreadAliveThreshold,
/// HAB_THREAD_ALIVE_THRESHOLD_SECS,
/// Duration::from_secs(5 * 60));
