Add source code URL cache mechanism

[kyoshidajp]

No description provided.

[github-actions]

Code Metrics Report

	main (d4ddbca)	#37 (9c756cf)	+/-
Coverage	54.1%	48.3%	-5.8%
Code to Test Ratio	1:0.5	1:0.5	-0.0
Test Execution Time	12s	15s	+3s

Details

  |                     | main (d4ddbca) | #37 (9c756cf) |  +/-  |
  |---------------------|----------------|---------------|-------|
- | Coverage            |          54.1% |         48.3% | -5.8% |
  |   Files             |             18 |            19 |    +1 |
  |   Lines             |            388 |           443 |   +55 |
+ |   Covered           |            210 |           214 |    +4 |
- | Code to Test Ratio  |          1:0.5 |         1:0.5 |  -0.0 |
  |   Code              |           1210 |          1322 |  +112 |
+ |   Test              |            656 |           657 |    +1 |
- | Test Execution Time |            12s |           15s |   +3s |

Code coverage of files in pull request scope (69.6% → 47.8%)

Files	Coverage	+/-
cmd/cache.go	0.0%	0.0%
cmd/diagnose.go	67.6%	-2.0%

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Reported by octocov