golang实现sql结果集以json格式输出的方法

func getJSON(sqlString string) (string,error) {
    stmt,err := db.Prepare(sqlString)
    if err != nil {
        return nil,err
    }
    defer stmt.Close()
    rows,err := stmt.Query()
    if err != nil {
        return nil,err
    }
    defer rows.Close()
    columns,err := rows.Columns()
    if err != nil {
      return "",err
    }
    count := len(columns)
    tableData := make([]map[string]interface{},0)
    values := make([]interface{},count)
    valuePtrs := make([]interface{},count)
    for rows.Next() {
      for i := 0; i < count; i++ {
          valuePtrs[i] = &values[i]
      }
      rows.Scan(valuePtrs...)
      entry := make(map[string]interface{})
      for i,col := range columns {
          var v interface{}
          val := values[i]
          b,ok := val.([]byte)
          if ok {
              v = string(b)
          } else {
              v = val
          }
          entry[col] = v
      }
      tableData = append(tableData,entry)
    }
    jsonData,err := json.Marshal(tableData)
    if err != nil {
      return "",err
    }
    fmt.Println(string(jsonData))
    return string(jsonData),nil
}