feat: implement database connection logic for SQL Server and Postgres

cmd/go_migrate/main.go

@@ -1,6 +1,15 @@
 package main
 
 import (
+	"context"
+	"database/sql"
+	"fmt"
+	"sync"
+	"time"
+
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
+	"github.com/jackc/pgx/v5/pgxpool"
+	_ "github.com/microsoft/go-mssqldb"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -8,5 +17,70 @@ func main() {
 	configureLog()
 	log.Info("Starting migration...")
 
+	var sourceDb *sql.DB
+	var targetDb *pgxpool.Pool
+
+	connectToDatabases(sourceDb, targetDb)
+
 	log.Info("Migration completed successfully!")
 }
+
+func connectToSqlServer() (*sql.DB, error) {
+	db, err := sql.Open("sqlserver", config.App.SourceDbUrl)
+	if err != nil {
+		return nil, fmt.Errorf("Unable to connect to sqlserver: %w", err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+	defer cancel()
+
+	if err := db.PingContext(ctx); err != nil {
+		return nil, fmt.Errorf("Unable to ping sqlserver: %w", err)
+	}
+
+	return db, nil
+}
+
+func connectToPostgres() (*pgxpool.Pool, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+	defer cancel()
+
+	pool, err := pgxpool.New(ctx, config.App.TargetDbUrl)
+	if err != nil {
+		return nil, fmt.Errorf("Unable to connect to postgres: %w", err)
+	}
+
+	if err := pool.Ping(ctx); err != nil {
+		pool.Close()
+		return nil, fmt.Errorf("Unable to ping postgres: %w", err)
+	}
+
+	return pool, nil
+}
+
+func connectToDatabases(sourceDb *sql.DB, targetDb *pgxpool.Pool) error {
+	var sourceDbErr, targetDbErr error
+	var wg sync.WaitGroup
+
+	wg.Go(func() {
+		sourceDb, sourceDbErr = connectToSqlServer()
+		if sourceDbErr != nil {
+			log.Error("Unable to connect to source db: ", sourceDbErr)
+		}
+	})
+
+	wg.Go(func() {
+		targetDb, targetDbErr = connectToPostgres()
+		if targetDbErr != nil {
+			log.Error("Unable to connect to target db: ", targetDbErr)
+		}
+	})
+
+	wg.Wait()
+
+	if sourceDbErr != nil || targetDbErr != nil {
+		return fmt.Errorf("Unable to connect to databases: %w (source), %w (target)", sourceDbErr, targetDbErr)
+	}
+
+	return nil
+}