database/sql: document expectations for named parameters

Require parameter names to not begin with a symbol.

Change-Id: I5dfe9d4e181f0daf71dad2f395aca41c68678cbe
Reviewed-on: https://go-review.googlesource.com/33493
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
index 27fb765..02746a2 100644
--- a/src/database/sql/sql_test.go
+++ b/src/database/sql/sql_test.go
@@ -486,8 +486,8 @@
 	rows, err := db.Query(
 		// Ensure the name and age parameters only match on placeholder name, not position.
 		"SELECT|people|age,name|name=?name,age=?age",
-		Named("?age", 2),
-		Named("?name", "Bob"),
+		Named("age", 2),
+		Named("name", "Bob"),
 	)
 	if err != nil {
 		t.Fatalf("Query: %v", err)