How to append URI as string in SQL query

Looks simple but I unable to make it happen. When browsing domain.com/post/1, it should show data from row id which value 1.

Row id is integer (int4).

Below the the codes, which is not working:

package main

import "fmt"
import "github.com/go-martini/martini"
import "net/http"
import "database/sql"
import _ "github.com/lib/pq"

func SetupDB() *sql.DB {
  db, err := sql.Open("postgres", "user=postgres password=apassword dbname=lesson4 sslmode=disable")
  PanicIf(err)
  return db
}

func PanicIf(err error) {
  if err != nil {
    panic(err)
  }
}

func main() {
  m := martini.Classic()
  m.Map(SetupDB())

  m.Get("/post/:idnumber", func(rw http.ResponseWriter, r *http.Request, db *sql.DB) {

    rows, err := db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)
    PanicIf(err)
    defer rows.Close()

    var title, author, description string
    for rows.Next() {
      err:= rows.Scan(&title, &author, &description)
      PanicIf(err)
      fmt.Fprintf(rw, "Title: %s\nAuthor: %s\nDescription: %s\n\n",
        title, author, description)
    }

  })

  m.Run()
}

Solution

Part of your issue is that you're using the string params["idnumber"] as part of the SQL query

db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)

That will look for a book where the id equals params["idnumber"] string.

What you need to do is use placeholders and the arguments according to http://golang.org/pkg/database/sql/#DB.Query

In this case your query should be

db.Query("SELECT title, author, description FROM books WHERE id=$1", params["idnumber"])

That should solve the issue I think you're having. However, until you actually update your question with the actual issue you're having I won't know.

Update

The error you're getting with undefined: params is because you don't have a params object in scope.

I'd suggest reading how martini works in regards of getting the arguments out of the route. https://github.com/go-martini/martini#routing