[hw-4] add postgres db

loms/internal/infra/postgres/postgres.go

@@ -0,0 +1,56 @@
+package postgres
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/pkg/errors"
+)
+
+// From https://gitlab.ozon.dev/go/classroom-18/students/week-4-workshop/-/blob/master/internal/infra/postgres/postgres.go
+
+func NewPool(ctx context.Context, dsn string) (*pgxpool.Pool, error) {
+	config, err := pgxpool.ParseConfig(dsn)
+	if err != nil {
+		return nil, errors.Wrap(err, "pgxpool.ParseConfig")
+	}
+
+	pool, err := pgxpool.NewWithConfig(ctx, config)
+	if err != nil {
+		return nil, errors.Wrap(err, "pgxpool.NewWithConfig")
+	}
+
+	return pool, nil
+}
+
+func NewPools(ctx context.Context, DSNs ...string) ([]*pgxpool.Pool, error) {
+	pools := make([]*pgxpool.Pool, len(DSNs))
+
+	for i, dsn := range DSNs {
+		cfg, err := pgxpool.ParseConfig(dsn)
+		if err != nil {
+			closeOpened(pools[:i])
+
+			return nil, errors.Wrap(err, "pgxpool.ParseConfig")
+		}
+
+		pool, err := pgxpool.NewWithConfig(ctx, cfg)
+		if err != nil {
+			closeOpened(pools[:i])
+
+			return nil, errors.Wrap(err, "pgxpool.NewWithConfig")
+		}
+
+		pools[i] = pool
+	}
+
+	return pools, nil
+}
+
+func closeOpened(pools []*pgxpool.Pool) {
+	for _, p := range pools {
+		if p != nil {
+			p.Close()
+		}
+	}
+}