Register pgx driver using major version

Fixed: #1480

stdlib/sql.go

@@ -58,6 +58,7 @@ import (
 	"math"
 	"math/rand"
 	"reflect"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -84,7 +85,13 @@ func init() {
 		configs: make(map[string]*pgx.ConnConfig),
 	}
 	fakeTxConns = make(map[*pgx.Conn]*sql.Tx)
-	sql.Register("pgx", pgxDriver)
+
+	drivers := sql.Drivers()
+	// if pgx driver was already registered by different pgx major version then we skip registration under the default name.
+	if i := sort.SearchStrings(sql.Drivers(), "pgx"); len(drivers) >= i || drivers[i] != "pgx" {
+		sql.Register("pgx", pgxDriver)
+	}
+	sql.Register("pgx/v4", pgxDriver)
 
 	databaseSQLResultFormats = pgx.QueryResultFormatsByOID{
 		pgtype.BoolOID:        1,

stdlib/sql_test.go

@@ -157,9 +157,22 @@ func closeStmt(t *testing.T, stmt *sql.Stmt) {
 }
 
 func TestSQLOpen(t *testing.T) {
-	db, err := sql.Open("pgx", os.Getenv("PGX_TEST_DATABASE"))
-	require.NoError(t, err)
-	closeDB(t, db)
+	tests := []struct {
+		driverName string
+	}{
+		{driverName: "pgx"},
+		{driverName: "pgx/v4"},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+
+		t.Run(tt.driverName, func(t *testing.T) {
+			db, err := sql.Open(tt.driverName, os.Getenv("PGX_TEST_DATABASE"))
+			require.NoError(t, err)
+			closeDB(t, db)
+		})
+	}
 }
 
 func TestNormalLifeCycle(t *testing.T) {