refactor: refactor timeout handling in timeout.go and timeout_test.go

[appleboy]

• Remove the import statement for "context" in timeout.go
• Remove the code block related to context cancellation in the New function in timeout.go
• Replace the case statement in the New function in timeout.go with a case statement using time.After
• Remove the import statement for "sync" in timeout_test.go
• Remove the TestDeadlineExceeded function in timeout_test.go

reverted PR #54

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (df5d291) 92.91% compared to head (f1ccf97) 94.91%. Report is 4 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #62 +/- ## ========================================== + Coverage 92.91% 94.91% +2.00% ========================================== Files 4 4 Lines 127 118 -9 ========================================== - Hits 118 112 -6 + Misses 6 4 -2 + Partials 3 2 -1 ``` | [Flag](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | Coverage Δ | | |---|---|---| | [go-](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | `94.91% <100.00%> (?)` | | | [go-1.18](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | `94.91% <100.00%> (+2.00%)` | :arrow_up: | | [go-1.19](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | `94.91% <100.00%> (+2.00%)` | :arrow_up: | | [go-1.20](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | `94.91% <100.00%> (?)` | | | [go-1.21](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | `89.83% <100.00%> (?)` | | | [macos-latest](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | `94.91% <100.00%> (?)` | | | [ubuntu-latest](https://app.codecov.io/gh/gin-contrib/timeout/pull/62/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib) | `94.91% <100.00%> (+2.00%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gin-contrib#carryforward-flags-in-the-pull-request-comment) to find out more.

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