add watchCancelDialContextTimeout const and notate why we have watchC…

…ancel on stmt

conn_go18.go

@@ -11,6 +11,10 @@ import (
 	"time"
 )
 
+const (
+	watchCancelDialContextTimeout = time.Second * 10
+)
+
 // Implement the "QueryerContext" interface
 func (cn *conn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {
 	list := make([]driver.Value, len(args))
@@ -117,7 +121,7 @@ func (cn *conn) watchCancel(ctx context.Context) func() {
 				// so it must not be used for the additional network
 				// request to cancel the query.
 				// Create a new context to pass into the dial.
-				ctxCancel, cancel := context.WithTimeout(context.Background(), time.Second*10)
+				ctxCancel, cancel := context.WithTimeout(context.Background(), watchCancelDialContextTimeout)
 				defer cancel()
 
 				_ = cn.cancel(ctxCancel)
@@ -213,6 +217,7 @@ func (st *stmt) ExecContext(ctx context.Context, args []driver.NamedValue) (driv
 	return st.Exec(list)
 }
 
+// watchCancel is implemented on stmt in order to not mark the parent conn as bad
 func (st *stmt) watchCancel(ctx context.Context) func() {
 	if done := ctx.Done(); done != nil {
 		finished := make(chan struct{})
@@ -223,7 +228,7 @@ func (st *stmt) watchCancel(ctx context.Context) func() {
 				// so it must not be used for the additional network
 				// request to cancel the query.
 				// Create a new context to pass into the dial.
-				ctxCancel, cancel := context.WithTimeout(context.Background(), time.Second*10)
+				ctxCancel, cancel := context.WithTimeout(context.Background(), watchCancelDialContextTimeout)
 				defer cancel()
 
 				_ = st.cancel(ctxCancel)