How to build a URL / Query in Golang

Background -

I need to build a URL / query based on user input from a form that will be used to make an API call.

Problem -

When building the URL, the params are not properly escaped. For example, the query "bad santa" ends up with a space between it instead of "+".

Current Output -
> e.g. https://api.example.org/3/search/movie?query=bad
> santa&api_key=#######

Expected Output -
> e.g. https://api.example.org/3/search/movie?query=bad+santa&api_key=#######

Code Example -

Root URL -

var SearchUrl = "https://www.example.org/3/search/movie?query="

Get params taken from user input -

var MovieSearch []string = r.Form["GetSearchKey"]  

API Key -

var apiKey = "&api_key=######"

I am using the ArrayToString() to parse the form input data

func ArrayToString(array []string) string{
    str := strings.Join(array, "+")
    return str 
}

Then building the URL -

var SearchUrl = "https://api.example.org/3/search/movie?query="
var MovieSearch []string = r.Form["GetSearchKey"]  
var apiKey = "&api_key=########"
UrlBuild := []string {SearchUrl, ArrayToString(MovieSearch), apiKey}
OUTPUT_STRING := ArrayToString(UrlBuild)

Question -

How to build a URL with user input GET params that are escaped properly?

Normally, one should use url package's Values.

Here's an example, that does what I think you want, on play
Both a simple main, and in http.HandlerFunc form:

package main

import "fmt"
import "net/url"
import "net/http"

func main() {
	baseURL := "https://www.example.org/3/search/movie"
	v := url.Values{}
	v.Set("query", "this is a value")
	perform := baseURL + "?" + v.Encode()
	fmt.Println("Perform:", perform)
}

func formHandler(w http.ResponseWriter, r *http.Request) {
	baseURL := "https://www.example.org/3/search/movie"
	v := url.Values{}
	
	v.Set("query", r.Form.Get("GetSearchKey")) // take GetSearchKey from submitted form
	v.Set("api_ley", "YOURKEY") // whatever your api key is
	
	perform := baseURL + "?" + v.Encode() // put it all together
	fmt.Println("Perform:", perform) // do something with it
}

Output:
Perform: https://www.example.org/3/search/movie?query=this+is+a+value

Notice how the values are put in to query string, properly escaped, for you.

You can escape parameters using https://golang.org/pkg/net/url/#QueryEscape, instead of doing it yourself.

Besides you should be using https://golang.org/pkg/net/url/#URL to build up your url:

params := fmt.Sprintf("?query=%s&api_key=######", url.QueryEscape("name"))
perform := url.URL{
	Scheme: 	"https",  
    Host: 		"api.example.com",
    Path:		"3/search/movie",
    RawQuery: 	params,
}

fmt.Println(perform) // <- Calls .String()

I recommend to check https://golang.org/doc/effective_go.html.

If your data comes in []string:

func ArrayToQuery(values []string) string {
	return url.QueryEscape(strings.Join(values, " "))
}

If MovieSearch contains one element with the value "bad santa", what you're seeing looks correct. It's joining those three strings and putting "+" between them.

If there is a space in the word you will need to replace it.

Example

package main

import (
	"fmt"
	"strings"
)

func main() {
	fmt.Println(strings.Replace("bad santa", " ", "+", -1))
}

So you should probably do it like this

func main() {
    a := []string{"bad", "santa"}
    fmt.Printf("%q\n", a)
    j := ArrayToString(a)
    strings.Replace(j, " ", "+",-1)
    fmt.Printf("%q\n", j)
}

Here is a link to the Go Documentation - https://golang.org/pkg/strings/#Replace