fix(chore): Wrong panic in singleflight #1349

Job	Run time
Check that Souin build as caddy module	6m 48s
Check that Souin build as middleware / Check that Souin build as Beego middleware	3m 23s
Check that Souin build as middleware / Check that Souin build as Dotweb middleware	3m 20s
Check that Souin build as middleware / Check that Souin build as Chi middleware	3m 42s
Check that Souin build as middleware / Check that Souin build as Echo middleware	3m 21s
Check that Souin build as middleware / Check that Souin build as Fiber middleware	3m 46s
Check that Souin build as middleware / Check that Souin build as Gin middleware	3m 22s
Check that Souin build as middleware / Check that Souin build as Goa middleware	3m 44s
Check that Souin build as middleware / Check that Souin build as Hertz middleware	3m 12s
Check that Souin build as middleware / Check that Souin build as Go-zero middleware	4m 59s
Check that Souin build as middleware / Check that Souin build as Kratos middleware	3m 37s
Check that Souin build as middleware / Check that Souin build as Roadrunner middleware	4m 49s
Check that Souin build as middleware / Check that Souin build as Souin middleware	3m 27s
Check that Souin build as middleware / Check that Souin build as Traefik middleware	2m 27s
Check that Souin build as middleware / Check that Souin build as Tyk middleware	5m 2s
Check that Souin build as middleware / Check that Souin build as Webgo middleware	3m 22s
	1h 2m 21s

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