🩹 Fix: behavior of `DefaultCtx.Fresh` when 'Last-Modified' and 'If-Modified-Since' are equal (#3150)

* fix(ctx): 'if-modified-since' and 'last-modified' are equal, `DefaultCtx.Fresh` now returns true

* accurate benchmark measurements

ctx.go

@@ -624,7 +624,7 @@ func (c *DefaultCtx) Fresh() bool {
 				if err != nil {
 					return false
 				}
-				return lastModifiedTime.Before(modifiedSinceTime)
+				return lastModifiedTime.Compare(modifiedSinceTime) != 1
 			}
 		}
 	}

ctx_test.go

@@ -1397,6 +1397,10 @@ func Test_Ctx_Fresh(t *testing.T) {
 	require.False(t, c.Fresh())
 
 	c.Request().Header.Set(HeaderIfModifiedSince, "Wed, 21 Oct 2015 07:28:00 GMT")
+	require.True(t, c.Fresh())
+
+	c.Request().Header.Set(HeaderIfModifiedSince, "Wed, 21 Oct 2015 07:27:59 GMT")
+	c.Response().Header.Set(HeaderLastModified, "Wed, 21 Oct 2015 07:28:00 GMT")
 	require.False(t, c.Fresh())
 }
 
@@ -1412,6 +1416,18 @@ func Benchmark_Ctx_Fresh_WithNoCache(b *testing.B) {
 	}
 }
 
+// go test -v -run=^$ -bench=Benchmark_Ctx_Fresh_LastModified -benchmem -count=4
+func Benchmark_Ctx_Fresh_LastModified(b *testing.B) {
+	app := New()
+	c := app.AcquireCtx(&fasthttp.RequestCtx{})
+
+	c.Response().Header.Set(HeaderLastModified, "Wed, 21 Oct 2015 07:28:00 GMT")
+	c.Request().Header.Set(HeaderIfModifiedSince, "Wed, 21 Oct 2015 07:28:00 GMT")
+	for n := 0; n < b.N; n++ {
+		c.Fresh()
+	}
+}
+
 // go test -run Test_Ctx_Binders -v
 func Test_Ctx_Binders(t *testing.T) {
 	t.Parallel()