Level 1: CLI Task Tracker (Core Go & Testing)

Welcome to your first Go hands-on challenge! Your goal is to build a Command Line Interface (CLI) application to track tasks, persisted as JSON.

Features to Implement

Your application must support the following CLI commands:

1. Add a task:

   go run main.go add "Buy groceries"
   # Output: Task added successfully with ID 1
   

2. List all tasks:

   go run main.go list
   # Output:
   # ID  Description    Status      Created At
   # 1   Buy groceries  [Pending]   2026-07-07 17:15:00
   

3. Complete a task:

   go run main.go complete 1
   # Output: Task 1 marked as completed
   

4. Delete a task:

   go run main.go delete 1
   # Output: Task 1 deleted
   

Storage & Persistence

• All tasks must be stored in a file named tasks.json in the current working directory.
• If tasks.json does not exist, the app should initialize an empty database.
• The tasks must be saved dynamically after every add, complete, or delete action.

---

Python vs Go Cheatsheet for this Project

Here is how you would map typical Python patterns to Go for this project:

1. JSON Serialization

• Python:

  import json
  # Write
  with open("tasks.json", "w") as f:
      json.dump(tasks, f, indent=4)
  # Read
  with open("tasks.json", "r") as f:
      tasks = json.load(f)
  

• Go:

  import "encoding/json"
  import "os"
  
  // Write
  data, err := json.MarshalIndent(tasks, "", "  ")
  if err != nil {
      return err
  }
  err = os.WriteFile("tasks.json", data, 0644)
  
  // Read
  data, err := os.ReadFile("tasks.json")
  if err != nil {
      if os.IsNotExist(err) {
          // Handle file not existing (first run)
      }
      return err
  }
  err = json.Unmarshal(data, &tasks)
  

2. Classes vs Structs

• Python:

  class Task:
      def __init__(self, id, description):
          self.id = id
          self.description = description
          self.done = False
  

• Go:

  // Fields MUST be capitalized (exported) to be visible to the encoding/json package!
  type Task struct {
      ID          int       `json:"id"`
      Description string    `json:"description"`
      Done        bool      `json:"done"`
      CreatedAt   time.Time `json:"created_at"`
  }
  

3. Error Handling

• Python:

  def get_task(id):
      if id not in tasks:
          raise ValueError("Task not found")
      return tasks[id]
  

• Go:

  import "errors"
  
  func (tm *TaskManager) GetTask(id int) (Task, error) {
      task, exists := tm.tasks[id]
      if !exists {
          return Task{}, errors.New("task not found")
      }
      return task, nil
  }
  

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Getting Started

1. Check out task.go. We have defined the skeleton structure and function signatures.
2. Check out task_test.go, which has standard tests.
3. Run the tests (they will fail initially because the methods are not implemented):

   /usr/local/go/bin/go test -v ./level1_task_tracker/...
   

4. Implement the methods in task.go.
5. Once your tests pass, write main.go to handle the command-line CLI interface.