first commit of restructured project

trahn-trade-backend/internal/db/connection.go

@@ -0,0 +1,49 @@
+package db
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+func Connect(dsn string) (*pgxpool.Pool, error) {
+	cfg, err := pgxpool.ParseConfig(dsn)
+	if err != nil {
+		return nil, fmt.Errorf("parse dsn: %w", err)
+	}
+
+	cfg.MaxConns = 20
+	cfg.MinConns = 2
+	cfg.MaxConnIdleTime = 30 * time.Second
+	cfg.MaxConnLifetime = 5 * time.Minute
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	p, err := pgxpool.NewWithConfig(ctx, cfg)
+	if err != nil {
+		return nil, fmt.Errorf("create pool: %w", err)
+	}
+
+	if err := p.Ping(ctx); err != nil {
+		p.Close()
+		return nil, fmt.Errorf("ping: %w", err)
+	}
+
+	return p, nil
+}
+
+func TestConnection(p *pgxpool.Pool) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+
+	var now time.Time
+	err := p.QueryRow(ctx, "SELECT NOW()").Scan(&now)
+	if err != nil {
+		return fmt.Errorf("test query: %w", err)
+	}
+	fmt.Printf("[DB] Connection successful at %s\n", now.Format(time.RFC3339))
+	return nil
+}