Add custom data to pgconn.PgConn

https://github.com/jackc/pgx/issues/1896

pgconn/pgconn.go

@@ -82,6 +82,8 @@ type PgConn struct {
 	slowWriteTimer    *time.Timer
 	bgReaderStarted   chan struct{}
 
+	customData map[string]any
+
 	config *Config
 
 	status byte // One of connStatus* constants
@@ -278,6 +280,7 @@ func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig
 	pgConn := new(PgConn)
 	pgConn.config = config
 	pgConn.cleanupDone = make(chan struct{})
+	pgConn.customData = make(map[string]any)
 
 	var err error
 	network, address := NetworkAddress(fallbackConfig.Host, fallbackConfig.Port)
@@ -1868,6 +1871,11 @@ func (pgConn *PgConn) SyncConn(ctx context.Context) error {
 	return errors.New("SyncConn: conn never synchronized")
 }
 
+// CustomData returns a map that can be used to associate custom data with the connection.
+func (pgConn *PgConn) CustomData() map[string]any {
+	return pgConn.customData
+}
+
 // HijackedConn is the result of hijacking a connection.
 //
 // Due to the necessary exposure of internal implementation details, it is not covered by the semantic versioning
@@ -1880,6 +1888,7 @@ type HijackedConn struct {
 	TxStatus          byte
 	Frontend          *pgproto3.Frontend
 	Config            *Config
+	CustomData        map[string]any
 }
 
 // Hijack extracts the internal connection data. pgConn must be in an idle state. SyncConn should be called immediately
@@ -1902,6 +1911,7 @@ func (pgConn *PgConn) Hijack() (*HijackedConn, error) {
 		TxStatus:          pgConn.txStatus,
 		Frontend:          pgConn.frontend,
 		Config:            pgConn.config,
+		CustomData:        pgConn.customData,
 	}, nil
 }
 
@@ -1921,6 +1931,7 @@ func Construct(hc *HijackedConn) (*PgConn, error) {
 		txStatus:          hc.TxStatus,
 		frontend:          hc.Frontend,
 		config:            hc.Config,
+		customData:        hc.CustomData,
 
 		status: connStatusIdle,
 

pgconn/pgconn_test.go

@@ -3185,6 +3185,22 @@ func TestConnOnPgError(t *testing.T) {
 	assert.True(t, pgConn.IsClosed())
 }
 
+func TestConnCustomData(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
+	defer cancel()
+
+	pgConn, err := pgconn.Connect(ctx, os.Getenv("PGX_TEST_DATABASE"))
+	require.NoError(t, err)
+	defer closeConn(t, pgConn)
+
+	pgConn.CustomData()["foo"] = "bar"
+	assert.Equal(t, "bar", pgConn.CustomData()["foo"])
+
+	ensureConnValid(t, pgConn)
+}
+
 func Example() {
 	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
 	defer cancel()