gogoproto

package main

import (
	"fmt"

	pbtypes "github.com/gogo/protobuf/types"
	"github.com/rvolosatovs/lorawan-stack/v3/pkg/gogoproto"
)

func main() {
	type cityDetails struct {
		Name string `protobuf:"name=name_city"`
	}

	type place struct {
		NameOfTheRegion string `protobuf:"name=name_region"`

		CityDetails cityDetails `protobuf:"bytes,name=city"`
	}

	london := place{
		CityDetails: cityDetails{Name: "London"},
	}
	holland := place{
		NameOfTheRegion: "Holland",
	}

	fields := gogoproto.GoFieldsPaths(&pbtypes.FieldMask{
		Paths: []string{"city.name_city"},
	}, london)
	fmt.Println(fields)

	fields = gogoproto.GoFieldsPaths(&pbtypes.FieldMask{
		Paths: []string{"name_region"},
	}, holland)
	fmt.Println(fields)

}

Output:

[CityDetails.Name]
[NameOfTheRegion]