tsk-13: Retrieve scheduled message endpoint (#36)

Closes #13

Reviewed-on: phoenix/textsender-api#36
Co-authored-by: phoenix <kundeng00@pm.me>
Co-committed-by: phoenix <kundeng00@pm.me>

internal/handler/helper.go

@@ -1,8 +1,11 @@
 package handler
 
-import "encoding/json"
-import "log"
-import "net/http"
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+)
 
 func ExtractFromRequest(r *http.Request, reqItem interface{}) error {
 	err := json.NewDecoder(r.Body).Decode(&reqItem)
@@ -21,3 +24,18 @@ func RespondWithJSON(w http.ResponseWriter, statusCode int, data interface{}) {
 		log.Printf("Error encoding JSON: %v", err)
 	}
 }
+
+// Gets the query parameter from the URL
+func ParseQueryParams(r *http.Request, query string) (*string, error) {
+	queryParams := r.URL.Query()
+	if _, exists := queryParams[query]; exists {
+		value := queryParams.Get(query)
+		if len(value) == 0 {
+			return nil, fmt.Errorf("Value of query parameter is empty")
+		} else {
+			return &value, nil
+		}
+	} else {
+		return nil, fmt.Errorf("Could not find query %s", query)
+	}
+}