feat: add ID function

gomockctx_test.go

@@ -0,0 +1,41 @@
+package gomockctx
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestID(t *testing.T) {
+	tests := []struct {
+		name string
+		ctx  context.Context
+		want string
+	}{
+		{
+			name: "nil",
+			ctx:  nil,
+			want: "",
+		},
+		{
+			name: "without ID",
+			ctx:  context.Background(),
+			want: "",
+		},
+		{
+			name: "with ID",
+			ctx: context.WithValue(
+				context.Background(), ctxKey, contextValue("xI2UWC8MvdYcU22B"),
+			),
+			want: "xI2UWC8MvdYcU22B",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := ID(tt.ctx)
+
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}