start working in the database connection

cmd/api/main.go

@@ -1,12 +1,16 @@
 package main
 
 import (
+	"context"
+	"database/sql"
 	"flag"
 	"fmt"
 	"log"
 	"net/http"
 	"os"
 	"time"
+
+	_ "github.com/lib/pq"
 )
 
 const version = "1.0.0"
@@ -14,6 +18,9 @@ const version = "1.0.0"
 type config struct {
 	port int
 	env  string
+	db   struct {
+		dsn string
+	}
 }
 
 type application struct {
@@ -26,10 +33,19 @@ func main() {
 
 	flag.IntVar(&cfg.port, "port", 4000, "API Server Port")
 	flag.StringVar(&cfg.env, "env", "development", "Environment (development|staging|production")
+	flag.StringVar(&cfg.db.dsn, "db-dsn", "postgres://postgres:superpassword@localhost/postgres?sslmode=disable", "PostgreSQL DSN")
 	flag.Parse()
 
 	logger := log.New(os.Stdout, "", log.Ldate|log.Ltime)
 
+	db, err := openDB(cfg)
+	if err != nil {
+		logger.Fatal(err)
+	}
+
+	defer db.Close()
+	logger.Printf("database connection pool established")
+
 	app := &application{
 		config: cfg,
 		logger: logger,
@@ -44,6 +60,23 @@ func main() {
 	}
 
 	logger.Printf("starting %s server on %s", cfg.env, srv.Addr)
-	err := srv.ListenAndServe()
+	err = srv.ListenAndServe()
 	logger.Fatal(err)
 }
+
+func openDB(cfg config) (*sql.DB, error) {
+	db, err := sql.Open("postgres", cfg.db.dsn)
+	if err != nil {
+		return nil, err
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	err = db.PingContext(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return db, nil
+}

go.mod

@@ -2,4 +2,7 @@ module greenlight.ergz
 
 go 1.21
 
-require github.com/julienschmidt/httprouter v1.3.0 // indirect
+require (
+	github.com/julienschmidt/httprouter v1.3.0 // indirect
+	github.com/lib/pq v1.10.9 // indirect
+)

go.sum

@@ -1,2 +1,4 @@
 github.com/julienschmidt/httprouter v1.3.0 h1:U0609e9tgbseu3rBINet9P48AI/D3oJs4dN7jwJOQ1U=
 github.com/julienschmidt/httprouter v1.3.0/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=
+github.com/lib/pq v1.10.9 h1:YXG7RB+JIjhP29X+OtkiDnYaXQwpS4JEWq7dtCCRUEw=
+github.com/lib/pq v1.10.9/go.mod h1:AlVN5x4E4T544tWzH6hKfbfQvm3HdbOxrmggDNAPY9o=