Ensure unique memory address for context Keys

.github/workflows/build-test.yaml

@@ -8,7 +8,7 @@ on:  # yamllint disable-line rule:truthy
     branches:
       - "*"
 env:
-  GO_VERSION: "~1.23.4"
+  GO_VERSION: "~1.24.13"
 jobs:
   unit:
     name: "Unit"

.github/workflows/lint.yaml

@@ -8,7 +8,7 @@ on:  # yamllint disable-line rule:truthy
   pull_request:
     branches: ["*"]
 env:
-  GO_VERSION: "~1.23.4"
+  GO_VERSION: "~1.24.13"
 jobs:
   lint:
     name: "Lint"

context.go

@@ -21,7 +21,9 @@ type ContextSet[V any] interface {
 
 // Key is a type that is used as a key in a context.Context for a
 // specific type of value V.
-type Key[V any] struct{}
+type Key[V any] struct {
+	_ int // ensures each instance has a unique address
+}
 
 // New creates a new Key
 func New[V any]() *Key[V] {

context_test.go

@@ -233,3 +233,30 @@ func expectPanic(t testing.TB, f func()) {
 	}()
 	wg.Wait()
 }
+
+func TestKeyUniqueness(t *testing.T) {
+	// Create two separate keys with the same type
+	key1 := New[string]()
+	key2 := New[string]()
+
+	// These should be different keys
+	if key1 == key2 {
+		t.Fatal("two separate keys have the same memory address!")
+	}
+
+	// They should store independent values
+	ctx := context.Background()
+	ctx = key1.Set(ctx, "value1")
+	ctx = key2.Set(ctx, "value2")
+
+	// Each key should retrieve its own value
+	val1, ok1 := key1.Value(ctx)
+	if !ok1 || val1 != "value1" {
+		t.Fatalf("key1 should return 'value1', got %q (ok=%v)", val1, ok1)
+	}
+
+	val2, ok2 := key2.Value(ctx)
+	if !ok2 || val2 != "value2" {
+		t.Fatalf("key2 should return 'value2', got %q (ok=%v)", val2, ok2)
+	}
+}

go.mod

@@ -1,3 +1,3 @@
 module github.com/authzed/ctxkey
 
-go 1.23.4
+go 1.24

magefiles/go.work

@@ -1,4 +1,4 @@
-go 1.23.4
+go 1.24
 
 use (
 .