Fix variable name and error handling for caching

[goccy]

• Fix validation process for the variable name
• Cache error handling process of gRPC method calling for multiple calling

[github-actions[bot]]

Code Metrics Report

	main (f6e7a58)	#229 (4e60ffe)	+/-
Coverage	65.5%	65.6%	+0.0%
Code to Test Ratio	1:0.3	1:0.3	-0.0
Test Execution Time	7m17s	7m3s	-14s

Details

``` diff | | main (f6e7a58) | #229 (4e60ffe) | +/- | |---------------------|----------------|----------------|-------| + | Coverage | 65.5% | 65.6% | +0.0% | | Files | 71 | 71 | 0 | | Lines | 11799 | 11817 | +18 | + | Covered | 7730 | 7747 | +17 | - | Code to Test Ratio | 1:0.3 | 1:0.3 | -0.0 | | Code | 36764 | 37060 | +296 | + | Test | 12853 | 12873 | +20 | + | Test Execution Time | 7m17s | 7m3s | -14s | ```

Code coverage of files in pull request scope (82.1% → 82.2%)

Files	Coverage	+/-
resolver/context.go	85.0%	-1.0%
resolver/resolver.go	82.1%	+0.1%

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Reported by octocov

[github-actions[bot]]

Code Metrics Report

	main (b7aa0a6)	#229 (9a8bf50)	+/-
Coverage	65.5%	65.6%	+0.0%
Code to Test Ratio	1:0.3	1:0.3	-0.0
Test Execution Time	7m15s	6m49s	-26s

Details

``` diff | | main (b7aa0a6) | #229 (9a8bf50) | +/- | |---------------------|----------------|----------------|-------| + | Coverage | 65.5% | 65.6% | +0.0% | | Files | 71 | 71 | 0 | | Lines | 11813 | 11831 | +18 | + | Covered | 7739 | 7756 | +17 | - | Code to Test Ratio | 1:0.3 | 1:0.3 | -0.0 | | Code | 36804 | 37119 | +315 | + | Test | 12870 | 12890 | +20 | + | Test Execution Time | 7m15s | 6m49s | -26s | ```

Code coverage of files in pull request scope (82.0% → 82.1%)

Files	Coverage	+/-
resolver/context.go	85.0%	-1.0%
resolver/resolver.go	82.1%	+0.1%

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Reported by octocov