feat: config initialization routines

modules/server/main.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"reflect"
+
+	"github.com/gin-gonic/gin"
+	"github.com/pelletier/go-toml/v2"
+	log "github.com/sirupsen/logrus"
+)
+
+var AppConfig Config
+
+func main() {
+	if len(os.Args) != 2 {
+		AppConfig.Mode = "env"
+	} else {
+		AppConfig.Mode = "argv"
+	}
+
+	err := InitConfig()
+	if err != nil {
+		log.Fatalf("Failed to init config: %v\n", err)
+	}
+
+	r := gin.Default()
+
+	r.LoadHTMLGlob("templates/*")
+
+	r.GET("/", func(c *gin.Context) {
+		c.HTML(http.StatusOK, "index.html", gin.H{
+			"title":   "Welcome Page",
+			"message": "Hello, Gin with HTML templates!",
+		})
+	})
+
+	r.Run(":8080")
+}
+
+func InitConfig() error {
+	if AppConfig.Mode == "argv" {
+		content, err := os.ReadFile(os.Args[1])
+		if err != nil {
+			return err
+		}
+
+		toml.Unmarshal(content, &AppConfig)
+
+		fmt.Printf("%+v\n", AppConfig)
+
+		return nil
+	} else if AppConfig.Mode == "env" {
+		f := reflect.ValueOf(AppConfig)
+
+		for i := 0; i < f.NumField(); i++ {
+			field := f.Type().Field(i)
+			tag := field.Tag
+			env_var := tag.Get("env")
+			fmt.Printf("Field: %v.\nEnvironment variable: %v.\n", field.Name, env_var)
+			if env_var != "" {
+				env_value, exists := os.LookupEnv(env_var)
+				if !exists {
+					return fmt.Errorf("there is no env variable %s", env_var)
+				}
+				err := setField(&AppConfig, field.Name, env_value)
+				if err != nil {
+					return fmt.Errorf("failed to set config field %s: %v", field.Name, err)
+				}
+			}
+		}
+
+		return nil
+	} else {
+		return fmt.Errorf("incorrect config mode")
+	}
+}