feat: initial FRED API Proxy project

- Go web server using Gin framework
- Proxy FRED economic data API
- Support series, observations, search, releases endpoints

main.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"fred-api/config"
+	"fred-api/handlers"
+
+	"github.com/gin-gonic/gin"
+	"github.com/joho/godotenv"
+)
+
+func main() {
+	if err := godotenv.Load(); err != nil {
+		log.Println("No .env file found, using default config")
+	}
+
+	cfg := config.Load()
+
+	fredHandler := handlers.NewFREDHandler(cfg)
+
+	gin.SetMode(gin.ReleaseMode)
+	router := gin.Default()
+
+	router.Use(func(c *gin.Context) {
+		c.Header("Access-Control-Allow-Origin", "*")
+		c.Header("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
+		c.Header("Access-Control-Allow-Headers", "Content-Type, Authorization")
+		if c.Request.Method == "OPTIONS" {
+			c.AbortWithStatus(204)
+			return
+		}
+		c.Next()
+	})
+
+	router.GET("/health", fredHandler.HealthCheck)
+
+	api := router.Group("/api/v1")
+	{
+		api.GET("/series", fredHandler.GetSeries)
+		api.GET("/series/observations", fredHandler.GetObservations)
+		api.GET("/series/search", fredHandler.SearchSeries)
+		api.GET("/releases", fredHandler.GetReleases)
+		api.GET("/releases/dates", fredHandler.GetReleaseDates)
+		api.GET("/release/series", fredHandler.GetReleaseSeries)
+	}
+
+	go func() {
+		fmt.Printf("FRED API Server starting on :%s\n", cfg.ServerPort)
+		fmt.Printf("FRED API Base URL: %s\n", cfg.FREDBaseURL)
+		fmt.Println("\nAvailable endpoints:")
+		fmt.Println("  GET /health              - Health check")
+		fmt.Println("  GET /api/v1/series                    - Get series info")
+		fmt.Println("  GET /api/v1/series/observations       - Get observations")
+		fmt.Println("  GET /api/v1/series/search             - Search series")
+		fmt.Println("  GET /api/v1/releases                  - Get all releases")
+		fmt.Println("  GET /api/v1/releases/dates            - Get release dates")
+		fmt.Println("  GET /api/v1/release/series            - Get series in release")
+		fmt.Println("")
+		fmt.Println("Examples:")
+		fmt.Println("  curl 'http://localhost:" + cfg.ServerPort + "/api/v1/series?series_id=GNPCA'")
+		fmt.Println("  curl 'http://localhost:" + cfg.ServerPort + "/api/v1/series/observations?series_id=GNPCA&limit=10'")
+		fmt.Println("  curl 'http://localhost:" + cfg.ServerPort + "/api/v1/series/search?search_text=GDP'")
+		fmt.Println("")
+
+		if err := router.Run(":" + cfg.ServerPort); err != nil {
+			log.Fatalf("Failed to start server: %v", err)
+		}
+	}()
+
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
+	<-quit
+
+	fmt.Println("\nShutting down server...")
+}