How to test mysql insert method

I'm setting up testing in Go. I use go-sqlmock to test mysql connection. Now I try to test mysql insert logic. But the error occurs.
I want to know how to resolve this error.

server side: golang
db: mysql
web framework: gin

dao.go

func PostDao(db *sql.DB, article util.Article, uu string) {
    ins, err := db.Prepare("INSERT INTO articles(uuid, title,content) VALUES(?,?,?)")
    if err != nil {
        log.Fatal(err)
    }
    ins.Exec(uu, article.TITLE, article.CONTENT)
}

dao_test.go

func TestPostArticleDao(t *testing.T) {
    db, mock, err := sqlmock.New()

    if err != nil {
        t.Fatalf("an error '%s' was not expected when opening a stub database connection", err)
    }

    defer db.Close()

    mock.ExpectExec("^INSERT INTO articles*").
        WithArgs("bea1b24d-0627-4ea0-aa2b-8af4c6c2a41c", "test", "test").
        WillReturnResult(sqlmock.NewResult(1, 1))

    article := util.Article{
        ID:      1,
        TITLE:   "test",
        CONTENT: "test",
    }

    PostDao(db, article, "bea1b24d-0627-4ea0-aa2b-8af4c6c2a41c")

    if err := mock.ExpectationsWereMet(); err != nil {
        t.Errorf("there were unfulfilled expections: %s", err)
    }
}

I expect go test -v runs without error.
But the actual is not.
Here is the error.

=== RUN   TestPostArticleDao
2019/08/31 00:08:11 call to Prepare statement with query 'INSERT INTO articles(uuid, title,content) VALUES(?,?,?)', was not expected, next expectation is: ExpectedExec => expecting Exec or ExecContext which:
  - matches sql: 'INSERT INTO articles(uuid, title,content) VALUES(?,?,?)'
  - is with arguments:
    0 - bea1b24d-0627-4ea0-aa2b-8af4c6c2a41c
    1 - test
    2 - test
  - should return Result having:
      LastInsertId: 1
      RowsAffected: 1
exit status 1
FAIL    article/api/dao 0.022s