The go-grpc-middleware retry middleware has a function perCallContext that calls context.WithTimeout and ignores the returned cancel function. According to the context.WithTimeout docs:

// Canceling this context releases resources associated with it, so code should
// call cancel as soon as the operations running in this Context complete:
//
// func slowOperationWithTimeout(ctx context.Context) (Result, error) {
// ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
// defer cancel() // releases resources if slowOperation completes before timeout elapses
// return slowOperation(ctx)
// }

Here is the offending code in https://github.com/grpc-ecosystem/go-grpc-middleware/blob/master/retry/retry.go#L290

func perCallContext(parentCtx context.Context, callOpts *options, attempt uint) context.Context {
	ctx := parentCtx
	if callOpts.perCallTimeout != 0 {
		ctx, _ = context.WithTimeout(ctx, callOpts.perCallTimeout)
	}
        ...