Guarantee sequential run for each operator

[k1LoW]

ref: #513

[github-actions]

Code Metrics Report

	main (68e8a82)	#562 (119381a)	+/-
Coverage	69.2%	69.2%	+0.0%
Code to Test Ratio	1:0.7	1:0.7	-0.0
Test Execution Time	2m45s	2m32s	-13s

Details

  |                     | main (68e8a82) | #562 (119381a) |  +/-  |
  |---------------------|----------------|----------------|-------|
+ | Coverage            |          69.2% |          69.2% | +0.0% |
  |   Files             |             49 |             49 |     0 |
  |   Lines             |           5062 |           5069 |    +7 |
+ |   Covered           |           3504 |           3510 |    +6 |
- | Code to Test Ratio  |          1:0.7 |          1:0.7 |  -0.0 |
  |   Code              |          10126 |          10137 |   +11 |
  |   Test              |           6850 |           6850 |     0 |
+ | Test Execution Time |          2m45s |          2m32s |  -13s |

Code coverage of files in pull request scope (81.2% → 81.3%)

Files	Coverage	+/-
operator.go	81.3%	+0.0%

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Reported by octocov