IMG-51: router -> server ns, handlers ns, added error to handler ret val (#1494)

* Introduced server, handlers, error ret in handlerfn

* Server struct with tests

* replace checkErr with return

server/timer_test.go

@@ -0,0 +1,67 @@
+package server
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCheckTimeout(t *testing.T) {
+	tests := []struct {
+		name  string
+		setup func() context.Context
+		fail  bool
+	}{
+		{
+			name:  "WithoutTimeout",
+			setup: context.Background,
+			fail:  false,
+		},
+		{
+			name: "ActiveTimerContext",
+			setup: func() context.Context {
+				req := httptest.NewRequest(http.MethodGet, "/test", nil)
+				newReq, _ := startRequestTimer(req)
+				return newReq.Context()
+			},
+			fail: false,
+		},
+		{
+			name: "CancelledContext",
+			setup: func() context.Context {
+				req := httptest.NewRequest(http.MethodGet, "/test", nil)
+				newReq, cancel := startRequestTimer(req)
+				cancel() // Cancel immediately
+				return newReq.Context()
+			},
+			fail: true,
+		},
+		{
+			name: "DeadlineExceeded",
+			setup: func() context.Context {
+				ctx, cancel := context.WithTimeout(context.Background(), time.Nanosecond)
+				defer cancel()
+				time.Sleep(time.Millisecond * 10) // Ensure timeout
+				return ctx
+			},
+			fail: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ctx := tt.setup()
+			err := CheckTimeout(ctx)
+
+			if tt.fail {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}