Change the behaviour of donegroup.Cancel significantly.

[k1LoW]

SSIA.

[github-actions]

Code Metrics Report

	main (d8095c1)	#47 (c251265)	+/-
Coverage	89.5%	91.2%	+1.6%
Code to Test Ratio	1:3.3	1:3.6	+0.2
Test Execution Time	2s	3s	+1s

Details

  |                     | main (d8095c1) | #47 (c251265) |  +/-  |
  |---------------------|----------------|---------------|-------|
+ | Coverage            |          89.5% |         91.2% | +1.6% |
  |   Files             |              1 |             1 |     0 |
  |   Lines             |            115 |           103 |   -12 |
- |   Covered           |            103 |            94 |    -9 |
+ | Code to Test Ratio  |          1:3.3 |         1:3.6 |  +0.2 |
  |   Code              |            232 |           204 |   -28 |
- |   Test              |            778 |           736 |   -42 |
- | Test Execution Time |             2s |            3s |   +1s |

Code coverage of files in pull request scope (89.5% → 91.2%)

Files	Coverage	+/-
donegroup.go	91.2%	+1.6%

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Reported by octocov