增加code coverage, 修复GetJob bug，增加devcontainer方便开发者

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 86.72%. Comparing base (c9eca56) to head (235e6ef).

Files	Patch %	Lines
dcron.go	66.66%	0 Missing and 1 partial :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #91 +/- ## =========================================== + Coverage 85.57% 86.72% +1.15% =========================================== Files 17 17 Lines 1102 1100 -2 =========================================== + Hits 943 954 +11 + Misses 126 111 -15 - Partials 33 35 +2 ```

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