feat: add config loading

config.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+type Config struct {
+	Apps map[string]App `json:"apps"`
+}
+
+type App struct {
+	ConfigPath string `json:"config_path"`
+}
+
+// Load config from file
+func LoadConfig(path string) (Config, error) {
+	configPath := getConfigPath(path)
+	f, err := os.Open(configPath)
+	if err != nil {
+		// https://github.com/golang/go/blob/3e1e13ce6d1271f49f3d8ee359689145a6995bad/src/os/error.go#L90-L91
+		if errors.Is(err, os.ErrNotExist) {
+			return Config{}, fmt.Errorf("file not exist %s: %w", configPath, err)
+		}
+	}
+	defer f.Close()
+
+	bytes, err := ioutil.ReadAll(f)
+	if err != nil {
+		return Config{}, fmt.Errorf("failed to read %s: %w", configPath, err)
+	}
+
+	var result Config
+	if err := json.Unmarshal(bytes, &result); err != nil {
+		return Config{}, fmt.Errorf("failed to unmarshal: %w,", err)
+	}
+
+	return result, nil
+}
+
+func getConfigPath(path string) string {
+	return filepath.Join(path, "configs/config.json")
+}