Implemented configuration file functionality

For site name, port number and data directory

config/config.go

@@ -0,0 +1,36 @@
+package config
+
+import (
+	"encoding/json"
+	"log"
+	"os"
+)
+
+type Config struct {
+	SiteName string `json:"site_name"`
+	Port     string `json:"port"`
+	DataDir  string `json:"data_dir"`
+}
+
+func Load(path string) Config {
+	configData := Config{
+		SiteName: "Unnamed Download Listing",
+		Port:     "8080",
+		DataDir:  "data",
+	}
+
+	file, err := os.Open(path)
+	if err != nil {
+		log.Println("No config file found, using defaults. Consider setting up a Site Name at the very least!")
+		return configData
+	}
+	defer file.Close()
+
+	// Overwrite the default configuration with data from 'file'
+	err = json.NewDecoder(file).Decode(&configData)
+	if err != nil {
+		log.Fatal("Config file exists but has errors:", err)
+	}
+
+	return configData
+}