[#91] Add support namespaces

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

internal/handler/middleware/util.go

@@ -0,0 +1,26 @@
+package middleware
+
+import (
+	"context"
+	"fmt"
+)
+
+// keyWrapper is wrapper for context keys.
+type keyWrapper string
+
+const nsKey = keyWrapper("namespace")
+
+// GetNamespace extract namespace from context.
+func GetNamespace(ctx context.Context) (string, error) {
+	ns, ok := ctx.Value(nsKey).(string)
+	if !ok {
+		return "", fmt.Errorf("couldn't get namespace from context")
+	}
+
+	return ns, nil
+}
+
+// SetNamespace sets namespace in the context.
+func SetNamespace(ctx context.Context, ns string) context.Context {
+	return context.WithValue(ctx, nsKey, ns)
+}