If rc.ErrShouldNotUseCache, skip all caching processes.

[k1LoW]

Previously, the cache process was passed through even if Cacher.Load returned rc.ErrShouldNotUseCache, but this fix skips it all.

[github-actions]

Code Metrics Report

	main (c46cabf)	#76 (5f390da)	+/-
Coverage	80.3%	60.8%	-19.5%
Code to Test Ratio	1:2.3	1:2.3	-0.0
Test Execution Time	37s	43s	+6s

Details

  |                     | main (c46cabf) | #76 (5f390da) |  +/-   |
  |---------------------|----------------|---------------|--------|
- | Coverage            |          80.3% |         60.8% | -19.5% |
  |   Files             |              7 |             7 |      0 |
  |   Lines             |            441 |           441 |      0 |
- |   Covered           |            354 |           268 |    -86 |
- | Code to Test Ratio  |          1:2.3 |         1:2.3 |   -0.0 |
  |   Code              |            727 |           729 |     +2 |
- |   Test              |           1690 |          1685 |     -5 |
- | Test Execution Time |            37s |           43s |    +6s |

Code coverage of files in pull request scope (80.4% → 47.5%)

Files	Coverage	+/-
rc.go	75.0%	+1.5%
testutil/cacher.go	0.0%	-91.7%

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Reported by octocov

[pyama86]

LGTM!!!!!!!!!!!!!!!!!!1