False-positive with a graceful shutdown

[AlekSi]

Simplified example:

// Run runs server until ctx is canceled, then stops it gracefully and exits.
func RunHandler(ctx context.Context) {
	s := http.Server{
		BaseContext: func(_ net.Listener) context.Context {
			return ctx
		},
	}

	go s.ListenAndServe()
	<-ctx.Done()

	// use new context for cancelation
	stopCtx, stopCancel := context.WithTimeout(context.Background(), time.Second) 
	defer stopCancel()
	s.Shutdown(stopCtx)

	s.Close()
}

stopCtx can't be inherited from ctx as the later is already canceled.

Maybe this linter can detect that <-ctx.Done() was already called by this point?

[nawa]

The same I faced with. It is more abstract example

package main

import (
	"context"
)

func main() {
	doSmth(context.Background())
}

func doSmth(ctx context.Context) {
	doSmth2(ctx)

	// I want to use context.Background() here
	ctx2, ctx2Cancel := context.WithCancel(context.Background())
	defer ctx2Cancel()

	doSmth2(ctx2)
}

func doSmth2(ctx context.Context) {
	_ = ctx
}

main.go:17:9: Non-inherited new context, use function like `context.WithXXX` instead (contextcheck)
        doSmth2(ctx2)

The issue occurs when context is provided into the function but I want to use another context instance intentionally. For example graceful shutdown should be done with Background context.

And currently there is no way to avoid this error from the linter

[kkHAIKE]

this case can write func like this to pass

func NoInheritCancel(_ context.Context) (context.Context,context.CancelFunc) {
  return context.WithCancel(context.Background())
}

[fedorkanin]

Shouldn't context.WithoutCancel(ctx) be used in this case? Docs. This way, we don't loose keys and values from parent context.

WithoutCancel returns a derived context that points to the parent context and is not canceled when parent is canceled. The returned context returns no Deadline or Err, and its Done channel is nil. Calling Cause on the returned context returns nil.

[AlekSi]

Shouldn't context.WithoutCancel(ctx) be used in this case?

Yes, but it did not exist in 2021