Coroutine part 1.

[codecov-commenter]

Codecov Report

Base: 64.25% // Head: 64.29% // Increases project coverage by +0.04% :tada:

Coverage data is based on head (09ed7b6) compared to base (23c53ab). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #84 +/- ## ========================================== + Coverage 64.25% 64.29% +0.04% ========================================== Files 4 4 Lines 1505 1507 +2 Branches 537 540 +3 ========================================== + Hits 967 969 +2 + Misses 47 43 -4 - Partials 491 495 +4 ``` | [Impacted Files](https://codecov.io/gh/BowenFu/hspp/pull/84?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bowen+Fu) | Coverage Δ | | |---|---|---| | [include/hspp.h](https://codecov.io/gh/BowenFu/hspp/pull/84/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bowen+Fu#diff-aW5jbHVkZS9oc3BwLmg=) | `75.97% <ø> (+0.05%)` | :arrow_up: | | [include/monadTrans.h](https://codecov.io/gh/BowenFu/hspp/pull/84/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bowen+Fu#diff-aW5jbHVkZS9tb25hZFRyYW5zLmg=) | `100.00% <ø> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bowen+Fu). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bowen+Fu)

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[BowenFu]

Fix #71

[BowenFu]

Fix #70