Callerによるパス解決サンプル

main.go

package main

import (
	"encoding/json"
	"io/ioutil"
	"log"
	"os"
	"path"
	"runtime"
)

type Config struct {
	Key1 string `json:"key1"`
	Key2 string `json:"key2"`
}

var Cfg Config

func main() {
	LoadConfigWithCaller("config/config.json")
	LoadConfig("config/config.json")
}

func LoadConfig(configPath string) {
	log.Printf("loading config file: %s", configPath)
	f, err := ioutil.ReadFile(configPath)
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}
	err = json.Unmarshal(f, &Cfg)
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}
	log.Printf("OK")
}

func LoadConfigWithCaller(configPath string) {
	_, filename, _, _ := runtime.Caller(1)
	path := path.Dir(filename) + "/" + configPath
	log.Printf("loading config (with caller) file: %s", path)
	f, err := ioutil.ReadFile(path)
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}
	err = json.Unmarshal(f, &Cfg)
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}
	log.Printf("OK")
}

$ ./main
2014/03/08 22:00:02 loading config (with caller) file: /private/tmp/caller_sample/config/config.json
2014/03/08 22:00:02 OK
2014/03/08 22:00:02 loading config file: config/config.json
2014/03/08 22:00:02 OK

$ cd ..
$ ./caller_sample/main
2014/03/08 22:00:12 loading config (with caller) file: /private/tmp/caller_sample/config/config.json
2014/03/08 22:00:12 OK
2014/03/08 22:00:12 loading config file: config/config.json
2014/03/08 22:00:12 open config/config.json: no such file or directory