👨🏻‍💻 Let’s walk through our Go project step-by-step. We're building a CLI note-taking tool

📁 Project Structure (2 files)

main.go

Handles:

• User input,
• Note creation,
• Displaying and saving the note.

note/note.go

Defines:

• The Note struct,
• Methods for displaying and saving,
• A constructor function New() for creating validated notes.

---

🧠 FILE 1: main.go

package main

Declares this as the main package, the entry point of the program.

✅ Imports

import (
	"bufio"
	"fmt"
	"os"
	"strings"
	"example.com/go-project/note"
)

• bufio, os: for reading input from terminal.
• strings: to trim newline characters.
• fmt: for printing output.
• note: custom module for handling notes.

---

🔹 getUserInput(prompt string) string

This function prints a prompt and reads the user's typed input.

reader := bufio.NewReader(os.Stdin)
text, err := reader.ReadString('\n')

• Uses bufio.NewReader for better line reading than fmt.Scanln.
• Trims \n or \r (cross-platform newline handling).

---

🔹 getNoteData() (string, string)

Prompts user for both title and content:

title := getUserInput("Note Title:")
content := getUserInput("Note Content:")
return title, content

---

🔹 main()

This is the driver logic:

title, content := getNoteData()

🔸 Create Note

userNote, err := note.New(title, content)

• Calls constructor from the note package.
• Validates empty fields.

🔸 Display Note

userNote.Display()

• Shows note title and content.

🔸 Save Note

err = userNote.Save()

• Writes the note to a .json file.

---

📁 FILE 2: note/note.go

package note

This is a custom package named note.

---

🧱 Struct Definition

type Note struct {
	Title     string    `json:"title"`
	Content   string    `json:"content"`
	CreatedAt time.Time `json:"created_at"`
}

A custom type Note with:

• Title (user-entered)
• Content (user-entered)
• CreatedAt (timestamp when note is created)

JSON tags make sure this struct is saved with the correct key names when encoded to JSON.

---

🔸 func (n Note) Display()

fmt.Printf("📝 Your note Titled %v has the following Content:\n\n%v\n", n.Title, n.Content)

• Method on Note
• Displays nicely formatted note in terminal

---

🔸 func (n Note) Save() error

fileName := strings.ReplaceAll(n.Title, " ", "_")
fileName = strings.ToLower(fileName) + ".json"

• Converts title like My Note to my_note.json

json, err := json.Marshal(n)

• Marshals (converts) Note struct to JSON

return os.WriteFile(fileName, json, 0644)

• Saves it to a file with read-write permission

---

🔸 func New(title, content string) (Note, error)

if title == "" || content == "" {
	return Note{}, errors.New("invalid input")
}

• Validates that both fields are not empty.

return Note{
	Title:     title,
	Content:   content,
	CreatedAt: time.Now(),
}, nil

• Returns a new note with current timestamp.

---

📂 Output Example

If the user enters:

Note Title: Grocery List
Note Content: Buy eggs, milk, and bread.

A file grocery_list.json is created:

{
  "title": "Grocery List",
  "content": "Buy eggs, milk, and bread.",
  "created_at": "2025-07-03T15:04:05Z"
}

---

🔄 Flow Summary

User Input ➜ Struct Creation ➜ JSON File Write

1. We get title & content via terminal
2. Validate and construct Note struct
3. Marshal it to JSON
4. Save to file

---