Fix cases where net conn write failure was not marking connection as dead

Also added loop to run these timing sensitive tests multiple times.

conn.go

@@ -483,6 +483,7 @@ func (c *Conn) Prepare(name, sql string) (ps *PreparedStatement, err error) {
 
 	_, err = c.conn.Write(wbuf.buf)
 	if err != nil {
+		c.die(err)
 		return nil, err
 	}
 
@@ -544,6 +545,7 @@ func (c *Conn) Deallocate(name string) (err error) {
 
 	_, err = c.conn.Write(wbuf.buf)
 	if err != nil {
+		c.die(err)
 		return err
 	}
 

conn_pool_test.go

@@ -229,6 +229,9 @@ func TestPoolAcquireAndReleaseCycleAutoConnect(t *testing.T) {
 func TestPoolReleaseDiscardsDeadConnections(t *testing.T) {
 	t.Parallel()
 
+	// Run timing sensitive test many times
+	for i := 0; i < 50; i++ {
+		func() {
 			maxConnections := 3
 			pool := createConnPool(t, maxConnections)
 			defer pool.Close()
@@ -288,6 +291,8 @@ func TestPoolReleaseDiscardsDeadConnections(t *testing.T) {
 			if stat.AvailableConnections != 0 {
 				t.Fatalf("Unexpected AvailableConnections: %v", stat.CurrentConnections)
 			}
+		}()
+	}
 }
 
 func TestConnPoolTransaction(t *testing.T) {

conn_test.go

@@ -945,6 +945,9 @@ func TestFatalRxError(t *testing.T) {
 func TestFatalTxError(t *testing.T) {
 	t.Parallel()
 
+	// Run timing sensitive test many times
+	for i := 0; i < 50; i++ {
+		func() {
 			conn := mustConnect(t, *defaultConnConfig)
 			defer closeConn(t, conn)
 
@@ -965,7 +968,9 @@ func TestFatalTxError(t *testing.T) {
 			}
 
 			if conn.IsAlive() {
-		t.Fatal("Connection should not be live but was")
+				t.Fatalf("Connection should not be live but was. Previous Query err: %v", err)
+			}
+		}()
 	}
 }