First attempt at splitting the Go code into seperate files to clean things up.

main.go

@@ -0,0 +1,189 @@
+package main
+
+import (
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+//Go Best practices: https://github.com/golovers/effective-go
+type Item struct {
+	Id                int32       `json:"id"`
+	Name              int32       `json:"name"`
+	ValueCents        int32       `json:"valueCents"`
+	PurchaseCostCents int32       `json:"purchasedCostCents"`
+	Aquired           time.Time   `json:"aquired"`
+	Description       string      `json:"description"`
+	Notes             string      `json:"notes"`
+	SoldForCents      int32       `json:"soldForCents"`
+	SoldTo            string      `json:"soldTo"`
+	Category          Category    `json:"category"`
+	Subcategory       Subcategory `json:"subcategory"`
+}
+
+func main() {
+	http.HandleFunc("/categories", categories)
+	http.HandleFunc("/category", category)
+	err := http.ListenAndServe(":8080", nil)
+
+	if err != nil {
+		panic(err)
+	}
+
+}
+
+func categories(w http.ResponseWriter, r *http.Request) {
+	switch r.Method {
+	case "GET":
+		getCategories(w, r)
+	default:
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		w.Write([]byte("Method not allowed"))
+	}
+}
+
+func category(w http.ResponseWriter, r *http.Request) {
+	switch r.Method {
+	case "GET":
+		getCategory(w, r)
+	case "POST":
+		insertCategory(w, r)
+	case "DELETE":
+		deleteCategory(w, r)
+	default:
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		w.Write([]byte("Method not allowed"))
+	}
+}
+
+func getCategory(w http.ResponseWriter, r *http.Request) {
+	id := r.URL.Query().Get("id")
+
+	value, err := strconv.ParseInt(id, 0, 64)
+
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	db := getSQLConnection()
+
+	defer db.Close()
+
+	var category Category
+
+	if err := db.QueryRow("SELECT * FROM category WHERE category_id = $1;", value).Scan(&category.Id, &category.Name); err != nil {
+		if err == sql.ErrNoRows {
+			w.Write([]byte("No rows found"))
+			return
+		}
+
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	jsonBytes, err := json.Marshal(&category)
+
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	w.Write(jsonBytes)
+}
+
+func deleteCategory(w http.ResponseWriter, r *http.Request) {
+	id := r.URL.Query().Get("id")
+
+	value, err := strconv.ParseInt(id, 0, 64)
+
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	db := getSQLConnection()
+
+	defer db.Close()
+
+	_, err = db.Exec("DELETE FROM category WHERE category_id = $1;", value)
+
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte(fmt.Sprintf("Deleted category '%d'.", value)))
+}
+
+func getCategories(w http.ResponseWriter, r *http.Request) {
+	categories := getAllCategories()
+
+	jsonBytes, err := json.Marshal(categories)
+
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("Failed to get a list of categories."))
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	w.Write(jsonBytes)
+}
+
+func insertCategory(w http.ResponseWriter, r *http.Request) {
+	ct := r.Header.Get("content-type")
+
+	if ct != "application/json" {
+		w.WriteHeader(http.StatusUnsupportedMediaType)
+		w.Write([]byte(fmt.Sprintf("Unsupported media type '%s'", ct)))
+		return
+	}
+
+	bodyBytes, err := ioutil.ReadAll(r.Body)
+
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte("Failed to parse request body"))
+		return
+	}
+
+	defer r.Body.Close()
+
+	var category Category
+
+	err = json.Unmarshal(bodyBytes, &category)
+
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte("Failed to unmarshal JSON"))
+		return
+	}
+
+	db := getSQLConnection()
+
+	defer db.Close()
+
+	id := 0
+
+	err = db.QueryRow("INSERT INTO category (category_name) VALUES ($1) RETURNING category_id;", category.Name).Scan(&id)
+
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte(fmt.Sprintf("New Record: %d", id)))
+}