Added configuration

config/config.go

@@ -0,0 +1,56 @@
+// Package config defines the configuration of our app
+package config
+
+import (
+	"log"
+	"os"
+	"sync"
+
+	"gopkg.in/yaml.v2"
+)
+
+type YamlBackend struct {
+	Path string `yaml:"path"`
+}
+
+// Configuration defines the base configuration of the expenses app
+type Configuration struct {
+	Port        string      `yaml:"port"`
+	AuthKey     string      `yaml:"authKey"`
+	DataBackend string      `yaml:"dataBackend"`
+	YamlBackend YamlBackend `yaml:"yamlBackend"`
+}
+
+var (
+	instance *Configuration
+	once     sync.Once
+	confPath string
+)
+
+// GetInstance returns the instance of the configuration of the app.
+func GetInstance() *Configuration {
+	once.Do(func() {
+		instance = &Configuration{}
+		instance.loadConfiguration()
+	})
+
+	return instance
+}
+
+// SetConfig sets the path for the configuration file.
+func SetConfig(path string) {
+	confPath = path
+}
+
+func (c *Configuration) loadConfiguration() {
+	file, err := os.ReadFile(confPath)
+	if err != nil {
+		log.Fatalf("Unable to open configuration file [%s]: %s", confPath,
+			err.Error())
+	}
+
+	err = yaml.Unmarshal(file, &instance)
+	if err != nil {
+		log.Fatalf("Error parsing JSON: %s", err.Error())
+	}
+}