reflect.PointerTo is supported only from go1.20, use a dummy variable…

… to get the pointer type

const.go

@@ -241,30 +241,48 @@ var DescRegex, _ = regexp.Compile(DESC_REGEX)
 var NilValue = reflect.Zero(reflect.TypeOf((*interface{})(nil)).Elem())
 
 var (
-	_typeOfInt     = reflect.TypeOf(0)
-	_typeOfInt8    = reflect.TypeOf(int8(0))
-	_typeOfInt16   = reflect.TypeOf(int16(0))
-	_typeOfInt32   = reflect.TypeOf(int32(0))
-	_typeOfInt64   = reflect.TypeOf(int64(0))
-	_typeOfUint    = reflect.TypeOf(uint(0))
-	_typeOfUint8   = reflect.TypeOf(uint8(0))
-	_typeOfUint16  = reflect.TypeOf(uint16(0))
-	_typeOfUint32  = reflect.TypeOf(uint32(0))
-	_typeOfUint64  = reflect.TypeOf(uint64(0))
-	_typeOfFloat32 = reflect.TypeOf(float32(0))
-	_typeOfFloat64 = reflect.TypeOf(float64(0))
+	// reflect.PointerTo is supported only from go1.20.
+	// So we use a dummy variable to get the pointer type.
+	_varInt     = 0
+	_varInt8    = int8(0)
+	_varInt16   = int16(0)
+	_varInt32   = int32(0)
+	_varInt64   = int64(0)
+	_varUint    = uint(0)
+	_varUint8   = uint8(0)
+	_varUint16  = uint16(0)
+	_varUint32  = uint32(0)
+	_varUint64  = uint64(0)
+	_varFloat32 = float32(0)
+	_varFloat64 = float64(0)
 )
+
+var (
+	_typeOfInt     = reflect.TypeOf(_varInt)
+	_typeOfInt8    = reflect.TypeOf(_varInt8)
+	_typeOfInt16   = reflect.TypeOf(_varInt16)
+	_typeOfInt32   = reflect.TypeOf(_varInt32)
+	_typeOfInt64   = reflect.TypeOf(_varInt64)
+	_typeOfUint    = reflect.TypeOf(_varUint)
+	_typeOfUint8   = reflect.TypeOf(_varUint8)
+	_typeOfUint16  = reflect.TypeOf(_varUint16)
+	_typeOfUint32  = reflect.TypeOf(_varUint32)
+	_typeOfUint64  = reflect.TypeOf(_varUint64)
+	_typeOfFloat32 = reflect.TypeOf(_varFloat32)
+	_typeOfFloat64 = reflect.TypeOf(_varFloat64)
+)
+
 var (
-	_typeOfIntPtr     = reflect.PointerTo(_typeOfInt)
-	_typeOfInt8Ptr    = reflect.PointerTo(_typeOfInt8)
-	_typeOfInt16Ptr   = reflect.PointerTo(_typeOfInt16)
-	_typeOfInt32Ptr   = reflect.PointerTo(_typeOfInt32)
-	_typeOfInt64Ptr   = reflect.PointerTo(_typeOfInt64)
-	_typeOfUintPtr    = reflect.PointerTo(_typeOfUint)
-	_typeOfUint8Ptr   = reflect.PointerTo(_typeOfUint8)
-	_typeOfUint16Ptr  = reflect.PointerTo(_typeOfUint16)
-	_typeOfUint32Ptr  = reflect.PointerTo(_typeOfUint32)
-	_typeOfUint64Ptr  = reflect.PointerTo(_typeOfUint64)
-	_typeOfFloat32Ptr = reflect.PointerTo(_typeOfFloat32)
-	_typeOfFloat64Ptr = reflect.PointerTo(_typeOfFloat64)
+	_typeOfIntPtr     = reflect.TypeOf(&_varInt)
+	_typeOfInt8Ptr    = reflect.TypeOf(&_varInt8)
+	_typeOfInt16Ptr   = reflect.TypeOf(&_varInt16)
+	_typeOfInt32Ptr   = reflect.TypeOf(&_varInt32)
+	_typeOfInt64Ptr   = reflect.TypeOf(&_varInt64)
+	_typeOfUintPtr    = reflect.TypeOf(&_varUint)
+	_typeOfUint8Ptr   = reflect.TypeOf(&_varUint8)
+	_typeOfUint16Ptr  = reflect.TypeOf(&_varUint16)
+	_typeOfUint32Ptr  = reflect.TypeOf(&_varUint32)
+	_typeOfUint64Ptr  = reflect.TypeOf(&_varUint64)
+	_typeOfFloat32Ptr = reflect.TypeOf(&_varFloat32)
+	_typeOfFloat64Ptr = reflect.TypeOf(&_varFloat64)
 )