How to Access Query Strings in Go's HTTP POST Requests?

Accessing Query Strings in POST Requests with Go's HTTP Package

When handling POST requests with Go's HTTP package, accessing and parsing query strings can be crucial. The HTTP package provides a convenient method for extracting query strings: Query().

In a POST request, the query string is typically attached to the URL, containing key-value pairs of information. The Query() method retrieves these key-value pairs and parses them into a Values map.

To access the query string in a POST request, follow these steps:

• Extract the URL: From the *http.Request object, obtain the URL using r.URL.
• Parse the Query String: Use the Query() method on the URL to parse the query string. This returns a Values map, where keys represent parameter names, and corresponding values are arrays of values for that parameter.
• Access Parameter Values: To retrieve parameter values from the Values map, use either the Get() or []string index notation.
• NOTE: Case-sensitivity is important when accessing parameter keys in the Values map.

For example:

func newHandler(w http.ResponseWriter, r *http.Request) {
  fmt.Println("GET params were:", r.URL.Query())

  // if only one expected
  param1 := r.URL.Query().Get("param1")
  if param1 != "" {
    // ... process it, will be the first (only) if multiple were given
    // note: if they pass in like ?param1=&param2= param1 will also be "" :|
  }

  // if multiples possible, or to process empty values like param1 in
  // ?param1=&param2=something
  param1s := r.URL.Query()["param1"]
  if len(param1s) > 0 {
    // ... process them ... or you could just iterate over them without a check
    // this way you can also tell if they passed in the parameter as the empty string
    // it will be an element of the array that is the empty string
  }    
}

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