Add a few notes regarding nil contexts

Signed-off-by: Cyril Cressent <cyril@sensu.io>

api/core/v2/multitenant.go

@@ -10,6 +10,8 @@ type MultitenantResource interface {
 // SetContextFromResource takes a context and a multi-tenant resource, adds the
 // namespace to the context, and returns the udpated context
 func SetContextFromResource(ctx context.Context, r MultitenantResource) context.Context {
+	// Here ctx can be nil, triggering the panic in Go 1.15. Maybe we can check
+	// if ctx is nil, and if so replace it with context.Background()
 	ctx = context.WithValue(ctx, NamespaceKey, r.GetNamespace())
 	return ctx
 }

backend/apid/graphql/handler.go

@@ -33,6 +33,7 @@ func (r *handlerImpl) Mutator(p graphql.ResolveParams) (interface{}, error) {
 		return nil, nil
 	}
 
+	// p.Context is nil here
 	ctx := corev2.SetContextFromResource(p.Context, src)
 	res, err := r.client.FetchMutator(ctx, src.Mutator)
 

backend/apid/graphql/handler_test.go

@@ -45,6 +45,9 @@ func TestHandlerTypeMutatorField(t *testing.T) {
 
 	// Success
 	client.On("FetchMutator", mock.Anything, mutator.Name).Return(mutator, nil).Once()
+	// We could add a Context: context.Background() to ResolveParams, but there
+	// might be other places in the code that instantiate a
+	// graphql.ResolveParams{} without a Context field?
 	res, err := impl.Mutator(graphql.ResolveParams{Source: handler})
 	require.NoError(t, err)
 	assert.NotEmpty(t, res)