config

cfg := config.Config{}
cfg.SetAccessorMode()
jsonPath, srcJSON := `$.a`, `{"a":1,"b":0}`
var src any
json.Unmarshal([]byte(srcJSON), &src)
output, err := jsonpath.Retrieve(jsonPath, src, cfg)
if err != nil {
	fmt.Printf(`type: %v, value: %v`, reflect.TypeOf(err), err)
	return
}
accessor := output[0].(config.Accessor)
srcMap := src.(map[string]any)

fmt.Printf("Get : %v\n", accessor.Get())

accessor.Set(2)
fmt.Printf("Set -> Src : %v\n", srcMap[`a`])

accessor.Set(3)
fmt.Printf("Set -> Get : %v\n", accessor.Get())

srcMap[`a`] = 4
fmt.Printf("Src -> Get : %v\n", accessor.Get())

Output:

Get : 1
Set -> Src : 2
Set -> Get : 3
Src -> Get : 4

config := config.Config{}
config.SetAggregateFunction(`max`, func(params []any) (any, error) {
	var result float64
	for _, param := range params {
		if floatParam, ok := param.(float64); ok {
			if result < floatParam {
				result = floatParam
			}
			continue
		}
		return nil, fmt.Errorf(`type error`)
	}
	return result, nil
})
jsonPath, srcJSON := `$[*].max()`, `[1,3]`
var src any
json.Unmarshal([]byte(srcJSON), &src)
output, err := jsonpath.Retrieve(jsonPath, src, config)
if err != nil {
	fmt.Printf(`type: %v, value: %v`, reflect.TypeOf(err), err)
	return
}
outputJSON, _ := json.Marshal(output)
fmt.Println(string(outputJSON))

Output:

[3]

config := config.Config{}
config.SetFilterFunction(`twice`, func(param any) (any, error) {
	if floatParam, ok := param.(float64); ok {
		return floatParam * 2, nil
	}
	return nil, fmt.Errorf(`type error`)
})
jsonPath, srcJSON := `$[*].twice()`, `[1,3]`
var src any
json.Unmarshal([]byte(srcJSON), &src)
output, err := jsonpath.Retrieve(jsonPath, src, config)
switch err.(type) {
case errors.ErrorFunctionNotFound:
	fmt.Printf(`type: %v, value: %v`, reflect.TypeOf(err), err)
	return
}
outputJSON, _ := json.Marshal(output)
fmt.Println(string(outputJSON))

Output:

[2,6]