fix(chore): Wrong panic in singleflight #1354

Job	Run time
Check that Souin build as caddy module	6m 34s
Check that Souin build as middleware / Check that Souin build as Dotweb middleware	2m 42s
Check that Souin build as middleware / Check that Souin build as Echo middleware	2m 43s
Check that Souin build as middleware / Check that Souin build as Chi middleware	2m 41s
Check that Souin build as middleware / Check that Souin build as Beego middleware	2m 37s
Check that Souin build as middleware / Check that Souin build as Fiber middleware	2m 46s
Check that Souin build as middleware / Check that Souin build as Goa middleware	2m 39s
Check that Souin build as middleware / Check that Souin build as Gin middleware	2m 31s
Check that Souin build as middleware / Check that Souin build as Go-zero middleware	3m 32s
Check that Souin build as middleware / Check that Souin build as Hertz middleware	2m 14s
Check that Souin build as middleware / Check that Souin build as Kratos middleware	2m 48s
Check that Souin build as middleware / Check that Souin build as Roadrunner middleware	3m 55s
Check that Souin build as middleware / Check that Souin build as Souin middleware	2m 36s
Check that Souin build as middleware / Check that Souin build as Traefik middleware	2m 18s
Check that Souin build as middleware / Check that Souin build as Tyk middleware	3m 20s
Check that Souin build as middleware / Check that Souin build as Webgo middleware	2m 34s
	48m 30s

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